tag:theconversation.com,2011:/au/topics/pigeons-1500/articlesPigeons – The Conversation2023-03-10T16:01:05Ztag:theconversation.com,2011:article/2013962023-03-10T16:01:05Z2023-03-10T16:01:05ZHow COVID lockdowns triggered changes in peregrine falcon diets – and what this means for urban pest control<figure><img src="https://images.theconversation.com/files/514683/original/file-20230310-104-4p8lml.jpg?ixlib=rb-1.1.0&rect=14%2C0%2C4910%2C3288&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Pigeons are a key source of food for the peregrine falcon.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/peregrine-falcon-spreading-wings-1658591701">Sriram Bird Photographer/Shutterstock</a></span></figcaption></figure><p>Many people <a href="https://theconversation.com/covid-19-reshaped-the-way-we-buy-prepare-and-consume-food-193069">saw their eating habits change</a> during the COVID-19 lockdowns. Some ate more frequently or experimented with healthier recipes. Others ordered more deliveries. </p>
<p>But human diets weren’t the only ones to change. In a <a href="https://besjournals.onlinelibrary.wiley.com/doi/full/10.1002/pan3.10445">recent study</a>, we found that lockdown triggered changes in the diets of London’s peregrine falcons. London is home to as many as <a href="https://www.nhm.ac.uk/discover/peregrine-falcons-and-their-city-success.html">30 breeding pairs of peregrines</a> (one of the world’s largest urban populations).</p>
<p>The emergence of high-definition web cameras now means that scientists can record every bit of food that peregrines feed to their young. Our team of 50 citizen scientists analysed live stream footage from peregrine nests across 27 English cities to determine what the birds were eating. We observed the nests throughout the 2020-2022 breeding seasons, allowing us to track the changes to their diets that occurred during and outside of lockdown periods.</p>
<p>In London, peregrines ate a lower proportion of feral pigeons (-15%) during the lockdowns. Instead, they caught more <a href="https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/starling-family/#:%7E:text=A%20family%20of%20small%20birds,wings%20and%20sharply%2Dpointed%20bills.">starlings</a> (+7%) and <a href="https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/ring-necked-parakeet/">ring-necked parakeets</a> (+3%).</p>
<p>Peregrine falcons depend on prey animals like pigeons for food. But, as pigeon populations themselves are contingent on humans, peregrines are vulnerable to changes in human activities. Our results demonstrate that humans are a key, but underappreciated, part of the ecology of urban environments.</p>
<h2>Bird watching, for science</h2>
<p>Pigeons – which descended from the cliff-dwelling <a href="https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/rock-dove/">rock dove</a> – have adopted our cities as their homes. In highly urbanised cities, humans support feral pigeons both intentionally and otherwise through the production of litter and food waste. These pigeons are now present in such vast numbers across London that <a href="https://londonist.com/2016/07/where-did-trafalgar-square-s-pigeons-come-from">feeding them is banned</a> in particular locations, including Trafalgar Square. </p>
<p><a href="https://www.meridianracingpigeons.com/raptorreport.pdf">Around 13 million</a> racing pigeons are also released into the wild in the UK each year – and some of them will turn up in our cities. Birds of prey subsequently catch <a href="https://www.rspb.org.uk/our-work/policy-insight/species/birds-of-prey-in-the-uk/racing-pigeons-and-birds-of-prey/">8% of these pigeons</a>. Yet, the importance of racing pigeons to the diet of urban peregrines remains uncertain. </p>
<p>When pandemic restrictions were imposed, the pigeon racing season was suspended and these birds were confined to their lofts. Feeding opportunities for feral pigeons also dwindled in urban areas as people were advised to stay at home. This forced hungry pigeons to spread out in search of alternative food sources, meaning fewer pigeons were present for peregrines to feed on. </p>
<p>The wide geographic coverage of our study also revealed that the effects of social restrictions on peregrine diets were uneven across the UK. London was the only city studied where the proportion of pigeons eaten dropped significantly. Across the other cities studied, pigeons took 0.3% more pigeons on average during lockdown periods than outside of them – an insignificant change.</p>
<p>This is likely due to London’s particularly large non-residential central area. The city’s core emptied as people stopped commuting and the <a href="https://www.nber.org/system/files/working_papers/w28876/w28876.pdf">food and retail sector ground to a halt</a>. So London’s pigeons had to cover more ground than their counterparts in smaller cities to reach residential areas where people could still feed them.</p>
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<img alt="Empty Westminster Bridge with the Houses of Parliament and the Big Ben in the background." src="https://images.theconversation.com/files/514661/original/file-20230310-462-fo17aa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514661/original/file-20230310-462-fo17aa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514661/original/file-20230310-462-fo17aa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514661/original/file-20230310-462-fo17aa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514661/original/file-20230310-462-fo17aa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514661/original/file-20230310-462-fo17aa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514661/original/file-20230310-462-fo17aa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Central London shut down during the COVID-19 lockdowns.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/empty-westminster-bridge-houses-parliament-big-242576479">pcruciatti/Shutterstock</a></span>
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<h2>Rethinking pest control</h2>
<p>Large pigeon flocks that are drawn to humans in parks or squabble over food waste at litter bins are familiar sights for city dwellers. We take these daily interactions for granted or see them as pests. But pigeons contribute to the success of apex predators like the peregrine falcon.</p>
<p>Pigeons are subject to pest control programmes globally. Countries like Singapore and Switzerland have opted to manage pigeon populations by targeting their human food sources. For example, the Swiss city of Basel <a href="https://www.nytimes.com/1993/02/09/science/science-watch-basel-solves-problem-of-too-many-pigeons.html">halved its street pigeon population</a> between 1988 and 1991 by prohibiting their feeding.</p>
<p>These measures are often imposed to improve public hygiene. <a href="https://www.jstor.org/stable/3782800">Research</a> has found that pigeons can pass infectious diseases like <a href="https://www.gov.uk/guidance/psittacosis">ornithosis</a> and <a href="https://www.ncbi.nlm.nih.gov/books/NBK567794/#:%7E:text=The%20Paramyxoviridae%20is%20a%20family,respiratory%20syncytial%20virus%20(RSV).">paramyxovirus</a> onto humans through their droppings. </p>
<p>Their excrement is also corrosive and can cause substantial damage to buildings. In 2003, the then Mayor of London Ken Livingston said pigeon droppings had caused <a href="http://news.bbc.co.uk/1/hi/england/london/3275233.stm">up to £140,000 worth of damage</a> to Nelson’s Column and other monuments in Trafalgar square. </p>
<p>But pigeon management overlooks the needs of the wildlife that share our cities. Our study offers a glimpse into how these efforts may have consequences for apex predators particularly in large cities, where the raptors may be more vulnerable to swings in the population of their pigeon prey. </p>
<p><a href="https://www.berghahnjournals.com/view/journals/nature-and-culture/12/2/nc120202.xml">Previous research</a> found that measures to control rat populations in the eastern US city of Philadelphia in 2013 forced red-tailed hawks to switch to eating pigeons, which they are poorly suited to catching. While London’s peregrines had starlings and parakeets as backup prey during lockdown, raptors in cities worldwide face the growing pressure of their prey being eradicated to protect humans from disease.</p>
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<img alt="A red tailed hawk in flight." src="https://images.theconversation.com/files/514662/original/file-20230310-20-93l8iu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514662/original/file-20230310-20-93l8iu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514662/original/file-20230310-20-93l8iu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514662/original/file-20230310-20-93l8iu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514662/original/file-20230310-20-93l8iu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514662/original/file-20230310-20-93l8iu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514662/original/file-20230310-20-93l8iu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The red tailed hawk – a bird of prey that is found through North America.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/red-tailed-hawk-flying-close-718914187">Justin Buchli/Shutterstock</a></span>
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<p>Given the importance of pest species to urban falcons, we must consider what could happen to urban raptor populations if these “undesirable” pest species are eradicated. The ecological impacts of the COVID-19 lockdowns remind us that we are part of urban ecosystems. Perhaps it’s time to reconsider how we co-exist with urban animals, working with rather than against them.</p><img src="https://counter.theconversation.com/content/201396/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brandon Mak received research funding from the British Trust for Ornithology and King's College London for this study. </span></em></p><p class="fine-print"><em><span>Ed Drewitt received a small grant from the British Trust for Ornithology to support the purchase of some equipment that supported this study.</span></em></p>Lockdown wasn’t good news for London’s peregrine falcons.Brandon Mak, PhD student in the Department of Geography, King's College LondonEd Drewitt, PhD student studying the diet of urban peregrines, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1717382021-11-15T20:00:44Z2021-11-15T20:00:44ZHow do pigeons find their way home? We looked in their ears with a diamond-based quantum microscope to find out<figure><img src="https://images.theconversation.com/files/431890/original/file-20211115-17-gnk7bt.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C2899%2C2133&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Homing pigeons are known for their uncanny ability to find their way home – navigating complex and changing landscapes. In fact, they do this so well they were used as a source of secure communication more than 2,000 years ago. </p>
<p>Julius Caesar <a href="https://www.asor.org/anetoday/2017/11/not-just-birds">reportedly sent</a> news of his conquest of Gaul back to Rome via pigeons, <a href="https://www.ft.com/content/255b75e0-c77d-11e2-be27-00144feab7de">as did Napoleon Bonaparte</a> following his defeat by England in the 1815 Battle of Waterloo. </p>
<p>We know pigeons use visual cues and can navigate based on landmarks along known travel routes. We also know they have a magnetic sense called “magnetoreception” which lets them navigate using Earth’s magnetic field. </p>
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Read more:
<a href="https://theconversation.com/explainer-how-do-homing-pigeons-navigate-25633">Explainer: how do homing pigeons navigate?</a>
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<p>But we don’t know exactly <em>how</em> they (and other species) do this. In <a href="https://www.pnas.org/cgi/doi/10.1073/pnas.2112749118">research</a> published today in the Proceedings of National Academy of Sciences, my colleagues and I tested a theory that attempts to link magnetoreception in homing pigeons with tiny lumps of iron-rich material found in their inner ears.</p>
<p>By using a new kind of magnetic microscope, we confirmed this isn’t the case. But the technology has opened the door for us to investigate the phenomenon in several other species. </p>
<h2>The current hypotheses</h2>
<p>Scientists have spent decades exploring the possible mechanisms for magnetoreception. There are currently two mainstream theories. </p>
<p>The first is a vision-based “free-radical pair” model. Homing pigeons and other migratory birds have proteins in the retina of their eyes called “cryptochromes”. These produce an electrical signal that <a href="https://www.nature.com/articles/s41586-021-03618-9">varies depending on the strength</a> of the local magnetic field.</p>
<p>This could potentially allow the birds to “see” Earth’s magnetic field, although scientists have yet to confirm this theory.</p>
<p>The second proposal for how homing pigeons navigate is based on lumps of magnetic material inside them, which may provide them with a magnetic particle-based directional compass.</p>
<p>We know magnetic particles are found in nature, in a group of bacteria called <a href="https://theconversation.com/magnetic-bacteria-and-their-unique-superpower-attract-researchers-100720">magnetotactic bacteria</a>. These bacteria produce magnetic particles and orient themselves along the Earth’s magnetic field lines.</p>
<p>Scientists are now looking for magnetic particles in a range of species. Potential candidates <a href="https://link.springer.com/article/10.1007%2Fs00114-007-0236-0">were found</a> in the upper beak of homing pigeons more than a decade ago, but <a href="https://www.nature.com/articles/nature11046">subsequent work</a> indicated these particles were related to iron storage and not magnetic sensing.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-evidence-for-a-human-magnetic-sense-that-lets-your-brain-detect-the-earths-magnetic-field-113536">New evidence for a human magnetic sense that lets your brain detect the Earth's magnetic field</a>
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<h2>A peek inside a pigeon’s ear</h2>
<p>The new search is now underway in the inner ear of pigeons, where iron particles known as “cuticulosomes” <a href="https://www.sciencedirect.com/science/article/pii/S0960982213004338">were first identified</a> in 2013. </p>
<p>Single cuticulosomes have been located within distinct regions in the pigeon inner ear where other known sensory systems exist (such as for hearing and balancing during flight). In theory, if there were a magnetic sensing system in pigeons, it should be located close to other sensory systems.</p>
<p>But to determine whether iron cuticulosomes can act as magnetoreceptors in pigeons, scientists need to determine their magnetic properties. This is no mean feat, since cuticulosomes are 1,000 times smaller than a grain of sand. </p>
<p>What’s more is they are only found in 30% of the hair cells within the inner ear, making them difficult to identify and characterise.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/431870/original/file-20211115-6434-uzv76r.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram showing a homing pigeon's inner ear, with labels for hair cells and magnetic particles." src="https://images.theconversation.com/files/431870/original/file-20211115-6434-uzv76r.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/431870/original/file-20211115-6434-uzv76r.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=595&fit=crop&dpr=1 600w, https://images.theconversation.com/files/431870/original/file-20211115-6434-uzv76r.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=595&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/431870/original/file-20211115-6434-uzv76r.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=595&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/431870/original/file-20211115-6434-uzv76r.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=748&fit=crop&dpr=1 754w, https://images.theconversation.com/files/431870/original/file-20211115-6434-uzv76r.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=748&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/431870/original/file-20211115-6434-uzv76r.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=748&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">We conducted quantum magnetic imaging of iron-organelles in the pigeon inner ear.</span>
<span class="attribution"><span class="source">Robert W de Gille</span>, <span class="license">Author provided</span></span>
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<p>To tackle this problem our group at the University of Melbourne, together with colleagues from Vienna’s Institute of Molecular Pathology and the Max Planck Society in Bonn, turned to a new imaging technology to explore the magnetic properties of iron cuticulosomes in the pigeon inner ear.</p>
<p>We developed a magnetic microscope that uses diamond-based sensors to visualise delicate magnetic fields emanating from tiny magnetic particles. </p>
<h2>Disproving the theory</h2>
<p>We carefully studied thin sections of the pigeon inner ear placed directly onto the diamond sensors. By applying magnetic fields of varying strengths to the tissue, we were able to gauge the magnetic susceptibility of single cuticulosomes.</p>
<p>Our results showed the magnetic properties of the cuticulosomes were not strong enough for them to act as a magnetic particle-based magnetoreceptor. In fact, the particles would need to be 100,000 times stronger to activate the sensory pathways required for magnetoreception in pigeons. </p>
<p>However, despite the search for the elusive magnetoreceptor coming up short, we are extremely excited by the potential of this magnetic microscope technology.</p>
<p>We hope to use it study a host of magnetic candidates across a variety of species including rodents, fish and turtles. And by doing so we can focus not only on cuticulosomes, but a range of other potentially magnetic particles.</p><img src="https://counter.theconversation.com/content/171738/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Simpson receives funding from the Australian Research Council. </span></em></p>In nature, one group of bacteria produces magnetic particles to orient themselves along Earth’s magnetic field lines.David Simpson, School of Physics, Senior Lecturer, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1269782019-12-09T15:57:05Z2019-12-09T15:57:05ZTurtle doves are disappearing from the UK – but there’s still hope for saving them<figure><img src="https://images.theconversation.com/files/305827/original/file-20191209-90592-13qiomc.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3726%2C2827&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Rebecca Young</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The 12 Days of Christmas is a song that promises a great deal, but there’s a line that carollers may have to omit in future. Before a whole house of leaping lords and dancing ladies, the second day is supposed to bring two turtle doves. But dramatic declines in populations across Europe may mean that day two disappoints true loves in Christmases to come.</p>
<p>Only slightly larger than a blackbird, the European turtle dove is the UK’s smallest species of pigeon, as well as its only migrant species. You would be hard pushed to find turtle doves in the UK during December, as they spend the winter in sub-Saharan Africa, returning to Europe to breed in late April. With their return comes their gentle purring song, a long-standing sign of spring.</p>
<p>Once widespread across England and Wales, the UK turtle dove population <a href="https://www.bto.org/research-data-services/publications/state-uk-birds/2017/state-uk-birds-2017">plummeted by 98% between 1970 and 2015</a>, with <a href="http://www.ebcc.info/index.php?ID=631">similar declines across Europe</a>. So what’s happening to this icon of the festive season?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/305830/original/file-20191209-90574-1hv81un.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/305830/original/file-20191209-90574-1hv81un.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/305830/original/file-20191209-90574-1hv81un.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=355&fit=crop&dpr=1 600w, https://images.theconversation.com/files/305830/original/file-20191209-90574-1hv81un.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=355&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/305830/original/file-20191209-90574-1hv81un.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=355&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/305830/original/file-20191209-90574-1hv81un.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=447&fit=crop&dpr=1 754w, https://images.theconversation.com/files/305830/original/file-20191209-90574-1hv81un.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=447&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/305830/original/file-20191209-90574-1hv81un.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=447&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The melody and early lyrics of ‘The 12 Days of Christmas’ song, recorded by Frank Kidson in the Leeds Mercury, 1891.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/The_Twelve_Days_of_Christmas_(song)#/media/File:Twelve_Days_of_Christmas_(Kidson).png">Frank Kidson</a></span>
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<h2>Dovetailing destruction</h2>
<p>Turtle doves only eat seeds, and their first choice is weed seeds. Since the second world war, farming has drastically intensified across Europe and while this has also increased food production, it has decimated the food sources of turtle doves and other farmland birds, mammals and insects. Cutting back wild field margins, increasing herbicide use and sowing crops in autumn instead of spring have all contributed to the disappearance of wildflowers. With less of this habitat and food available, species are forced to feed more on easily accessible, man-made food sites, like stored or spilt grain on farms and garden bird feeders.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/yellowhammer-the-brexit-bird-with-a-story-to-tell-about-the-eu-103066">Yellowhammer: the Brexit bird with a story to tell about the EU</a>
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<p>This has increased the risk of diseases spreading where birds congregate to feed. Just as diseases tend to spread on public transport, when large numbers of people come into close contact, the same is true for birds at garden feeders. Fewer wild sources of food are also blamed for the later arrival of turtle doves in Europe and their earlier migration to Africa, reducing their possible breeding time. Turtle doves can lay up to three clutches of eggs per season, but with less time to breed, they’re raising fewer chicks. As conservation scientists, we think this effect alone could explain most of the decline that’s been seen over the last 50 years.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/305868/original/file-20191209-90580-1whxs43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/305868/original/file-20191209-90580-1whxs43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/305868/original/file-20191209-90580-1whxs43.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/305868/original/file-20191209-90580-1whxs43.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/305868/original/file-20191209-90580-1whxs43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/305868/original/file-20191209-90580-1whxs43.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/305868/original/file-20191209-90580-1whxs43.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The UK countryside now offers few good places to eat and rest for turtle doves.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/farmers-harvesting-potato-crop-autumn-farm-1194113722?src=78f7655b-c14e-4598-9b64-c69b59ad578a-1-2">Ian_Sherriffs/Shutterstock</a></span>
</figcaption>
</figure>
<p>But turtle doves are also killed by recreational hunters, and although they’re widely protected, hunting was permitted in ten EU countries as recently as 2018, with <a href="https://www.realwire.com/releases/52-million-wild-birds-killed-by-European-hunters-per-year-new-study-reveals">more than a million birds killed</a> each year in France, Spain and Portugal, along the western migratory route which UK birds travel. Hunting at these levels is likely to prevent turtle dove populations from recovering, even with restrictions on the timing of hunting and the numbers of birds shot.</p>
<p>As migrants, turtle doves are threatened by what’s known as multiple jeopardy – they face challenges in African wintering grounds as well as in their European breeding grounds. Squeezed out of both habitats, migrant species tend to suffer more severe declines than their sedentary counterparts.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-breakdown-is-knocking-the-natural-world-out-of-sync-and-we-should-all-be-worried-123892">Climate breakdown is knocking the natural world out of sync – and we should all be worried</a>
</strong>
</em>
</p>
<hr>
<h2>How to help</h2>
<p>As a PhD candidate studying turtle doves, I’ve had the privilege of working with these beautiful birds in their natural habitat. I saw thousands of turtle doves leaving one prominent winter roosting site in Senegal – an amazing sight to behold, considering their rarity back in the UK. On a trip to Hungary, one of the only countries in Europe that’s home to a stable population of turtle doves, I heard them singing and saw pairs fluttering between trees. Having spent the majority of my time over the past two years reading about how poorly this species is faring, these moments were truly invigorating.</p>
<p>I’m hopeful that the work of <a href="https://www.operationturtledove.org/">Operation Turtle Dove</a>, an effort by four UK conservation organisations, can counter the problems facing the species. This includes helping farmers look after wildlife by reintroducing uncropped field margins where the plants that doves like to eat can grow. Conservationists are also working closely with hunting organisations in Europe to ensure the activity is sustainable. They’ve already succeeded in reducing the hunting allowance in France.</p>
<p>Anybody can help by simply reporting a turtle dove sighting on the <a href="https://www.bto.org/our-science/projects/birdtrack/about">British Trust for Ornithology’s BirdTrack website</a>. This can help target conservation efforts where they’ll have the greatest impact. <a href="https://www.operationturtledove.org/nature-enthusiasts/">Turtle dove-friendly habitats</a> can sprout up in British gardens and parks too, encouraging the spring visitors to feed and nest. All it takes is planting the food species they like, such as fumitory and red and white clover, or allowing hedges to grow for the birds to nesting.</p>
<p>If people act now, they can safeguard the purr of spring in the British countryside, and make sure no one goes empty handed on the second day of Christmas.</p><img src="https://counter.theconversation.com/content/126978/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rebecca Young receives funding from Natural Environment Research Council (NERC) and the Royal Society for the Protection of Birds (RSPB).</span></em></p>Farming and habitat destruction have caused the species to disappear from large areas of Europe.Rebecca Young, PhD Candidate in Conservation and Ecology, Cardiff UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/995652019-03-27T16:16:44Z2019-03-27T16:16:44ZPrinciple behind Google’s April Fools’ pigeon prank proves more than a joke<figure><img src="https://images.theconversation.com/files/264444/original/file-20190318-28499-66kcrw.jpg?ixlib=rb-1.1.0&rect=513%2C2506%2C3294%2C2255&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Consider the wisdom of the flock.</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/hPOFScEaZcA">Zac Ong/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><a href="https://archive.google.com/pigeonrank/">Google’s 2002 April Fools’ Day joke</a> purportedly disclosed that its popular search engine was not actually powered by artificial intelligence, but instead by biological intelligence. Google had deployed bunches of birds, dubbed pigeon clusters, to calculate the relative value of web pages because they proved to be faster and more reliable than either human editors or digital computers.</p>
<p>The joke hinged on the silliness of the premise – but the scenario does have more than a bit of the factual mixed in with the fanciful.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/264443/original/file-20190318-28512-g4b3sl.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264443/original/file-20190318-28512-g4b3sl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/264443/original/file-20190318-28512-g4b3sl.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=354&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264443/original/file-20190318-28512-g4b3sl.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=354&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264443/original/file-20190318-28512-g4b3sl.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=354&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264443/original/file-20190318-28512-g4b3sl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=445&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264443/original/file-20190318-28512-g4b3sl.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=445&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264443/original/file-20190318-28512-g4b3sl.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=445&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A screenshot of Google’s explanation of how PigeonRank supposedly worked.</span>
<span class="attribution"><a class="source" href="https://archive.google.com/pigeonrank/">Google</a></span>
</figcaption>
</figure>
<p>The prank had taken a page out of 20th-century behaviorist B. F. Skinner’s <a href="https://www.verywellmind.com/operant-conditioning-a2-2794863">operant conditioning</a> playbook by allegedly teaching pigeons to peck for a food reward whenever the birds detected a relevant search result.</p>
<p>It also adapted Victorian polymath Francis Galton’s <a href="https://doi.org/10.1038/075450a0">vox populi</a> – or the voice of the people – principle by purportedly putting the web search task to something of a vote. The more the flocks of pigeons pecked at a particular website, the higher it rose on the user’s results page. This so-called PigeonRank system thus rank-ordered a user’s search results in accord with the pecking order of Google’s suitably schooled birds.</p>
<p>More than a decade later, we integrated elements of this spoof into <a href="https://doi.org/10.1371/journal.pone.0141357">our own serious research project</a> using a real mini-flock of four pigeons. Our research team included <a href="https://health.ucdavis.edu/publish/providerbio/search/11653">a pathologist</a>, <a href="https://winshipcancer.emory.edu/bios/faculty/krupinski-elizabeth.html">a radiologist</a> and <a href="https://scholar.google.com/citations?user=SIl5WVYAAAAJ&hl=en">two experimental</a> <a href="https://scholar.google.com/citations?user=CiWDe9EAAAAJ&hl=en">psychologists</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/264174/original/file-20190315-28483-11dzk01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264174/original/file-20190315-28483-11dzk01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/264174/original/file-20190315-28483-11dzk01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=404&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264174/original/file-20190315-28483-11dzk01.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=404&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264174/original/file-20190315-28483-11dzk01.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=404&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264174/original/file-20190315-28483-11dzk01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=507&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264174/original/file-20190315-28483-11dzk01.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=507&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264174/original/file-20190315-28483-11dzk01.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=507&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The test chamber provided pigeons with an image to classify for the reward of a food pellet.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1371/journal.pone.0141357">PLoS ONE 10(11): e0141357</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Exploiting the well-established <a href="http://crosstalk.cell.com/blog/pigeons-arent-just-rats-with-wings">visual and cognitive prowess of pigeons</a>, we taught our birds to peck either a blue or a yellow button on a computerized touchscreen in order to categorize pathology slides that depicted either benign or cancerous human breast tissue samples.</p>
<p>In each training session, we showed pigeons several slides of each type in random order on the touchscreen. Pigeons first had to peck the pathology slide multiple times – this step encouraged the birds to study them. Then the two report buttons popped up on each side of the tissue sample. If the tissue sample looked benign and the pigeons pecked the “benign” report button or if the presented tissue sample looked malignant and the pigeons pecked the “malignant” report button, then they received a food reward. However, if the pigeons chose the incorrect report button, then no food was given.</p>
<p>After two weeks of training, the pigeons attained accuracy levels ranging between 85 and 90 percent correct. Granted, this accomplishment falls short of their reading human text – although time will tell if that too is within <a href="https://doi.org/10.1073/pnas.1607870113">the ken of pigeons</a> – but the pigeons were quite able to make such highly accurate reports despite considerable variations in the magnification of the slide images.</p>
<p>We went on to test the pigeons with brand-new images to see if the birds could reliably transfer what they had learned; this is the key criterion for claiming that they’d learned a generalized concept of “benign/malignant tissue samples.” Accuracy to the familiar training samples averaged around 85 percent correct, and accuracy to the novel testing samples was nearly as high, averaging around 80 percent correct. This high level of transfer indicates that rote memorization alone cannot explain the pigeon’s categorization proficiency.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/264435/original/file-20190318-28487-14ykryc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264435/original/file-20190318-28487-14ykryc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/264435/original/file-20190318-28487-14ykryc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=314&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264435/original/file-20190318-28487-14ykryc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=314&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264435/original/file-20190318-28487-14ykryc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=314&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264435/original/file-20190318-28487-14ykryc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=395&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264435/original/file-20190318-28487-14ykryc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=395&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264435/original/file-20190318-28487-14ykryc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=395&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pigeons were able to generalize the skill of classifying tissue samples.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1371/journal.pone.0141357">PLoS ONE 10(11): e0141357</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Finally, we put Google’s PigeonRank proposal to the test. With an expanded set of breast tissue samples, we assessed the accuracy of each of four pigeons against the “wisdom of the flock,” a technique we termed “flock-sourcing.” To calculate these “flock” scores, we assigned each trial a score of 100 percent if three or four pigeons correctly responded, and we assigned a score of 50 percent if two pigeons correctly responded. Three or four pigeons never incorrectly responded.</p>
<p>The accuracy scores of the four individual pigeons were 73, 79, 81 and 85 percent correct. However, the accuracy score of the “flock” was 93 percent, thereby exceeding that of every individual bird. Pigeons <a href="http://news.mit.edu/2017/algorithm-better-wisdom-crowds-0125">thus join people</a> in evidencing better wisdom from crowds. Playing on Galton’s original term, you might call this vox columbae – or the voice-of-the-pigeons principle.</p>
<p>Although all of this may seem to be a bit of feathery fluff, over the past several years our report has resonated across several fields, going beyond pathology and radiology to include the burgeoning realm of artificial intelligence. It has been recognized in several articles including one <a href="https://www.newyorker.com/magazine/2017/04/03/ai-versus-md">quoting Geoff Hinton</a>, a key figure behind modern AI: “The role of radiologists will evolve from doing perceptual things that could probably be done by a highly trained pigeon to doing far more cognitive things.” In other words, machines may eventually be programmed to match what pigeons can do, leaving the more interesting and challenging tasks to humans.</p>
<p>What began as an elaborate April Fools’ prank has thus proved to be more than a joke. Never underestimate the brains of birds. They’re really <a href="https://www.activewild.com/bird-intelligence/">brainy beasts</a>.</p><img src="https://counter.theconversation.com/content/99565/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>After Google suggested PigeonRank was at the root of its search function, a group of researchers put a small flock of the birds to a different classification test in real life.Edward Wasserman, Professor of Experimental Psychology, University of IowaRichard Levenson, Professor of Pathology and Laboratory Medicine, University of California, DavisVictor Navarro, Graduate Student in Psychology, University of IowaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1078492018-12-04T13:39:21Z2018-12-04T13:39:21ZWe’ve saved pink pigeons from extinction – now let’s be kinder to their grey cousins<figure><img src="https://images.theconversation.com/files/248823/original/file-20181204-34148-tiol5u.jpg?ixlib=rb-1.1.0&rect=3%2C356%2C2552%2C1555&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A pink pigeon in the wild of Mauritius.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/29229281@N00/6329183903">Arcalexx/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>There is a touch of the Dickensian about the urban pigeon, often seen hobbling about on gnarled stumps, pecking at trash. The mongrel mix of grey and brown plumage on feral pigeons adds to the dowdy look, the occasional iridescent flash on neck feathers too obvious, too cheap. Dickens himself wrote of the <a href="http://spitalfieldslife.com/2010/01/26/dickens-in-spitalfields/">pigeons of Spitalfields</a> in London, associated with the poorest hovels:</p>
<blockquote>
<p>The pigeon hutches and pigeon traps on the tops of poor dwelling. </p>
</blockquote>
<p>Our local shopping mall entrance regularly echoes to the wheeling scream of a recorded peregrine falcon, played purposefully to scare away the pigeons. Urban animal life, whether domestic or feral, has often been lumped in with the socially excluded – beggars, drunks and revellers and the like.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/248789/original/file-20181204-34157-8o59j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/248789/original/file-20181204-34157-8o59j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/248789/original/file-20181204-34157-8o59j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/248789/original/file-20181204-34157-8o59j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/248789/original/file-20181204-34157-8o59j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/248789/original/file-20181204-34157-8o59j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/248789/original/file-20181204-34157-8o59j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A couple of ‘feral’ pigeons.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/kissing-pigeons-feral-pigeon-columba-livia-450837580?src=IKiRrDIwf2Ajt7OoSaLbuQ-1-8">Cristian Gusa/Shutterstock</a></span>
</figcaption>
</figure>
<h2>The prettier pink cousin</h2>
<p>Meanwhile other pigeons provoke intense concern. The pink pigeon of Mauritius is a heartwarming example of what we can do to protect endangered species. In 1975 only ten birds lingered at just one site. It was listed by the IUCN as Critically Endangered in 1994 – “<a href="https://www.durrell.org/wildlife/species-index/pink-pigeon/timeline/%23myCarousel">possibly the most threatened bird in the world</a>”. Today there are <a href="https://news.mongabay.com/2018/11/two-iconic-birds-make-a-striking-comeback-but-much-work-remains/">around 400</a> in the wild of Mauritius. </p>
<p>This pigeon has some distinct advantages. It is pink, it lives on an exotic island famous for the Dodo and it has had some big-name backers – notably author Gerald Durrell, who brought some into captivity in 1976 to breed and started a programme of releasing them back into the wild – along with intensive habitat management.</p>
<p>As a result, the pink pigeon’s numbers and range have <a href="https://www.birdlife.org/worldwide/news/red-list-northern-bald-ibis-pink-pigeon-making-comeback">markedly increased</a>, with wild-bred young now turning up. Pink pigeons in Mauritius have turned the corner. Meanwhile their urban grey brethren remain every bit the unloved city mob.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/247769/original/file-20181128-32191-1ttna6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/247769/original/file-20181128-32191-1ttna6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/247769/original/file-20181128-32191-1ttna6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/247769/original/file-20181128-32191-1ttna6b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/247769/original/file-20181128-32191-1ttna6b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/247769/original/file-20181128-32191-1ttna6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/247769/original/file-20181128-32191-1ttna6b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/247769/original/file-20181128-32191-1ttna6b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">There were just ten pink pigeons left on Mauritius in 1990, now the population is stable at 400.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/1083289394?src=NtSN-TZ3T17H8AJE_Yspfg-1-0&size=huge_jpg">Peter Hatch/Shutterstock</a></span>
</figcaption>
</figure>
<h2>The beak shall inherit the Earth</h2>
<p>The urban pigeon is a great example of the <a href="https://www.theguardian.com/books/2017/sep/02/inheritors-of-the-earth-chris-d-thomas-review-gaia-vince">inheritors of the Earth</a> described by ecologist Chris Thomas – species that do well because of us, thriving in the world we have created. Theirs is a biodiversity of cityscapes, a zoopolis deserving of our respect. Not least because the rats, racoons and pigeons of our cities are so like us – at home in concrete landscapes and on diets of processed food.</p>
<p>I am not against the effort expended on the pink pigeon at all. They are cute and exotic, two prime criteria for conservation – but the urban pigeon deserves our respect too. The great shame is that other members of the pigeon family are also at risk, species that were once commonplace, which can hardly be said of the pink pigeon. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/where-are-all-the-dead-pigeons-98874">Where are all the dead pigeons?</a>
</strong>
</em>
</p>
<hr>
<p>Take the turtle dove, for example, which belongs to the <a href="https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/pigeons-and-doves/">same family as pigeons</a>. In the UK, the turtle dove population has declined by <a href="https://www.bto.org/sites/default/files/publications/state-of-uk-birds-_2017.pdf">more than 95% in barely two decades</a>. This once common farmland dove is a bird of high summer – its call is a sleepy drone on the hottest days. It is the dove of poetry and ballads, the <a href="https://www.poetryfoundation.org/poems/45085/the-phoenix-and-the-turtle-56d2246f86c06">Phoenix’s lover</a> in a Shakespeare sonnet.</p>
<p>We understandably focus so much effort on rare species while we don’t notice that the commonplace is in sharp decline. Thankfully, the turtle dove is now the focus of its own <a href="https://www.operationturtledove.org/get-involved/habitat/">conservation projects</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/247770/original/file-20181128-32214-qi2ujv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/247770/original/file-20181128-32214-qi2ujv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/247770/original/file-20181128-32214-qi2ujv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/247770/original/file-20181128-32214-qi2ujv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/247770/original/file-20181128-32214-qi2ujv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/247770/original/file-20181128-32214-qi2ujv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/247770/original/file-20181128-32214-qi2ujv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/247770/original/file-20181128-32214-qi2ujv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Two turtle doves.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/turtle-dove-european-streptopelia-turtur-591893375?src=tbWbksdU9J8psoHSalUl_A-1-11">Wildlife World/Shutterstock</a></span>
</figcaption>
</figure>
<h2>From charming Darwin to fine pets</h2>
<p>The urban pigeon needs no such help, although they have fallen from grace since the days when pigeon fancying was a widespread hobby, which even had Charles Darwin hooked. Pigeons in all their domestic variety feature large in <a href="https://www.allaboutbirds.org/darwins-other-bird-the-domestic-pigeon/">Darwin’s book</a>, The Variation of Animals and Plants Under Domestication.</p>
<p>Darwin installed a <a href="http://darwinspigeons.com/">pigeon breeding loft in his home</a> and gathered invaluable insights into how traits are inherited through reproduction by studying their breeding. Pigeons are likely to be more qualified muses for Darwin’s theories on evolution by natural selection than the commonly cited <a href="https://theconversation.com/charles-darwins-theory-of-evolution-owes-more-to-his-garden-than-the-galapagos-100984">Galapagos Island finches</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/humans-not-entirely-at-fault-for-passenger-pigeon-extinction-28024">Humans not entirely at fault for passenger pigeon extinction</a>
</strong>
</em>
</p>
<hr>
<p>The story lends a distinct air of erudite science and respectability to the gentlemen pigeon fanciers of Victorian times. Not so any more – pigeon fancying is now a peripheral pastime of a lost world of old men tending their pigeon crees in tucked away allotments and backyards.</p>
<p>Turtle doves and pink pigeons will always arouse our sympathy, while the dodo and passenger pigeon – once the most numerous bird in North America before <a href="https://theconversation.com/humans-not-entirely-at-fault-for-passenger-pigeon-extinction-28024">dying out in 1914</a> – stand as accusing witnesses. Meanwhile the feral pigeon battles on, hobbling, chased by kids, tormented by mall managers, <a href="https://www.youtube.com/watch?v=phUs2kIGY9M">swallowed whole by pelicans</a>. You can’t help but admire them.</p><img src="https://counter.theconversation.com/content/107849/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mike Jeffries does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Pink pigeons may make more charismatic subjects for our adoration, but their feral relatives who keep us company in towns and cities are just as deserving.Mike Jeffries, Associate Professor, Ecology, Northumbria University, NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1019322018-08-31T09:40:58Z2018-08-31T09:40:58ZCurious Kids: how do birds see where they’re going?<figure><img src="https://images.theconversation.com/files/234423/original/file-20180831-195310-14ehr2m.jpg?ixlib=rb-1.1.0&rect=235%2C538%2C4252%2C2940&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/racing-pigeon-poses-front-lens-camera-1091450942?src=AXEtGZkDRdVOgdEATmmYiA-2-11">Shutterstock.</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children of all ages. The Conversation is asking young people to send in questions they’d like an expert to answer. All questions are welcome: find out how to enter at the bottom.</em> </p>
<hr>
<blockquote>
<p><strong>We have eyes on the front of our heads so we can see where we are going, but birds’ eyes are on the side so how do they see where they’re going? – Thomas and Luke, age six, Sussex, UK</strong></p>
</blockquote>
<hr>
<p>Dear Thomas and Luke,</p>
<p>Thanks for your question. First of all, I should mention that not all birds have their eyes on the sides of their heads. Pigeons and parrots do, but other birds, such as owls, have large eyes placed close together at the front of their heads – a bit like ours. </p>
<p>Whether they have eyes at the front or on the sides of their heads, all birds can still see straight ahead. But that doesn’t mean all birds see things in the same way. In fact, where a bird’s eyes are on its head can tell us a lot about how it sees the world. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/234327/original/file-20180830-195298-1iingrq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/234327/original/file-20180830-195298-1iingrq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/234327/original/file-20180830-195298-1iingrq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/234327/original/file-20180830-195298-1iingrq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/234327/original/file-20180830-195298-1iingrq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/234327/original/file-20180830-195298-1iingrq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/234327/original/file-20180830-195298-1iingrq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Eyes to the front, owls!</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Having two eyes means animals can see a three dimensional image of what’s around them. So they can perceive the height, width and depth of an object, as well as how far away it is. </p>
<p>Where a bird’s eyes are on its head affects its field of vision – that’s how much it can see in front and to the side at any one time. Think about how far you can see to either side without turning your head: these are the limits of your own field of vision. </p>
<p>Because owls have eyes at the front of their heads, they have a smaller field of vision – around 150 degrees for a barn owl (though they can turn their heads very far to look around). </p>
<p>Parrots, pigeons and other birds with eyes on the sides of their heads have a much bigger field of vision, of about 300 degrees. Amazingly, this means that they can see in front and a long way to the side, at the same time. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/233907/original/file-20180828-86153-4paps.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/233907/original/file-20180828-86153-4paps.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=445&fit=crop&dpr=1 600w, https://images.theconversation.com/files/233907/original/file-20180828-86153-4paps.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=445&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/233907/original/file-20180828-86153-4paps.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=445&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/233907/original/file-20180828-86153-4paps.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=559&fit=crop&dpr=1 754w, https://images.theconversation.com/files/233907/original/file-20180828-86153-4paps.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=559&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/233907/original/file-20180828-86153-4paps.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=559&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A ring-necked parakeet with eyes on the side of its head.</span>
</figcaption>
</figure>
<p>Where the eyes are placed decides how a bird views its surroundings using different types of vision. Binocular vision means both eyes focus on the same object at the same time, and eye movement is coordinated – this is the kind of vision that predatory birds such as owls rely on most. </p>
<p>Monocular vision means each eye is focused on a different object at any particular moment, and this is normal for parrots and pigeons. Having different kinds of vision helps different kinds of birds survive in the wild.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/233912/original/file-20180828-86138-1607sr5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/233912/original/file-20180828-86138-1607sr5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=321&fit=crop&dpr=1 600w, https://images.theconversation.com/files/233912/original/file-20180828-86138-1607sr5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=321&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/233912/original/file-20180828-86138-1607sr5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=321&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/233912/original/file-20180828-86138-1607sr5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=403&fit=crop&dpr=1 754w, https://images.theconversation.com/files/233912/original/file-20180828-86138-1607sr5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=403&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/233912/original/file-20180828-86138-1607sr5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=403&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Different birds have different fields of vision.</span>
</figcaption>
</figure>
<p>For parrots and pigeons, having eyes on the sides of their heads is a huge advantage. Having a wider field of vision with only a small blind spot behind them lets these birds see where they are going, while also keeping an eye out for predators which might be trying to sneak up on them. </p>
<p>For predatory raptors such as barn owls, having forward-facing eyes helps them to see depth and distance much more clearly, since both eyes can focus on the same object at the same time. This is perfect for spotting and catching small prey such as field mice. </p>
<p>So though it might seem like birds with eyes on the side of their heads can’t see where they are going, they can see forward and sideways at the same time, and in fact can see much more than those with eyes facing forwards. </p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age and which town or city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question, but we will do our best.</em></p>
<hr>
<p><em>More <a href="https://theconversation.com/topics/curious-kids-36782?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Curious Kids</a> articles, written by academic experts:</em></p>
<ul>
<li><p><em><a href="https://theconversation.com/curious-kids-how-does-gravity-pull-things-down-to-earth-101545?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">How does gravity pull things down to Earth? – Gabriel, age 4, Stewartby, UK</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-what-sea-creature-can-attack-and-win-over-a-blue-whale-98551?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">What sea creature can attack and win over a blue whale? – Drake, age seven, Sydney, Australia</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-what-is-fire-100490?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">What is fire? – Lyra, age seven, Oxford, UK</a></em></p></li>
</ul><img src="https://counter.theconversation.com/content/101932/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hazel Jackson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Not all birds have eyes on the sides of their heads – but even those that do can see straight in front of them.Hazel Jackson, Affiliate, University of KentLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/988742018-06-27T13:42:48Z2018-06-27T13:42:48ZWhere are all the dead pigeons?<figure><img src="https://images.theconversation.com/files/224952/original/file-20180626-112614-1y2jwgo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">shutterstock</span> </figcaption></figure><p>It may not seem like one of life’s great mysteries, but a quick internet search reveals that people from across the world – London to Hong Kong, Cape Town to Buenos Aires – are asking this same question: for all the pigeons out there in our cities, where are all the dead ones? Alas they’re not pondering the presence of pigeon heaven, but rather, where are all the bodies? </p>
<p>Pigeons are as ubiquitous in the world’s cities as bad traffic, buskers, and late-night takeaways. London alone is estimated to contain more than <a href="http://www.londonpigeons.co.uk/">a million pigeons</a>, inhabiting the many parks and gardens that crisscross its 1,000 square miles. Given these vast numbers – and the fact that an urban pigeon seldom lives for more than three or four years – it’s a wonder why they are not strewn across city streets.</p>
<p>There are several possible reasons for this. First, pigeons are just one part of a wide array of creatures to have adopted our cities as their home. Foxes, rats, gulls, <a href="https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/crow-family/">crows and ravens</a> all do a wonderful job of cleaning up any carrion they come across, including deceased pigeons. These species perform inestimable services to the urban ecosystem, reducing human exposure to rotting matter and helping cut the transmission of infectious diseases.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/224687/original/file-20180625-19385-195a28.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/224687/original/file-20180625-19385-195a28.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/224687/original/file-20180625-19385-195a28.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/224687/original/file-20180625-19385-195a28.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/224687/original/file-20180625-19385-195a28.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/224687/original/file-20180625-19385-195a28.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/224687/original/file-20180625-19385-195a28.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Pigeons are the most common bird in London.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cute-little-boy-rubber-boots-feeding-367427291?src=CxmlJ70MMAnORWCyWkxRHA-1-10">shutterstock</a></span>
</figcaption>
</figure>
<p>Alongside these native janitors, domestic cats are equally happy to take care of a dead or injured pigeon. It is estimated that there are <a href="https://www.pfma.org.uk/cat-population-2016">half a million cats living in London alone</a> – roughly two pigeons per cat – and if you’re “lucky” they might bring one home as a present. Whether a resident moggy or some other carnivore, this network of surreptitious street cleaners will usually whisk away any pigeon corpses long before they’re seen by human eyes.</p>
<h2>High-rise hideaways</h2>
<p>Most pigeons, however, don’t simply drop dead on the ground. To understand where pigeons themselves are likely to go when feeling vulnerable or unwell, we need to delve into their origins. The pigeons we see in cities are domestic pigeons who have undergone some serious “rewilding”. They were originally bred as homing pigeons, trained birds who relayed important messages over large distances long before telephones. These pigeons even <a href="https://www.bbc.co.uk/news/uk-scotland-tayside-central-17138990">won prestigious medals</a> in both world wars.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/224684/original/file-20180625-19399-13ecj91.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/224684/original/file-20180625-19399-13ecj91.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/224684/original/file-20180625-19399-13ecj91.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/224684/original/file-20180625-19399-13ecj91.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/224684/original/file-20180625-19399-13ecj91.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/224684/original/file-20180625-19399-13ecj91.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/224684/original/file-20180625-19399-13ecj91.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">This rock pigeon just wants to die with dignity.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/front-view-face-rock-pigeon-facerock-1069354133?src=nx8EtRifn3tLp6adHTNQQA-1-25">shutterstock</a></span>
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<p>Going back further, the original homing pigeons were bred centuries ago from <a href="https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/rock-dove">wild rock doves</a>, a species which inhabits sea cliffs and coastal caves. Cities, with their high-rise buildings and elevated ledges, provide ideal nest sites for feral pigeons, and create an environment reminiscent of their ancestral homes. This background means that, when sick or injured, pigeons instinctively retreat to dark, remote places – ventilation systems, attics, building ledges – hoping to remain out of reach and unnoticed by predators. The predators don’t see them, but neither do we: often when pigeons expire, they are in hiding.</p>
<h2>Gone before their time</h2>
<p>But what actually causes a pigeon to die? As they get older, pigeons become more susceptible to disease, and often become slower to react to oncoming predators. It is well-established that when a predator attacks a flock of birds, slower individuals can become isolated from the group, making them easy prey. Dying of old age is not a luxury afforded to most pigeons: as soon as they shows signs of slowness or sickness, many are snapped up by <a href="http://www.bbc.co.uk/earth/story/20150626-the-predator-ruling-uk-city-skies">peregrine falcons</a>, sparrowhawks, or other predators.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/224696/original/file-20180625-19375-l7g61a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/224696/original/file-20180625-19375-l7g61a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/224696/original/file-20180625-19375-l7g61a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/224696/original/file-20180625-19375-l7g61a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/224696/original/file-20180625-19375-l7g61a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/224696/original/file-20180625-19375-l7g61a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/224696/original/file-20180625-19375-l7g61a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A peregrine falcon with its unfortunate quarry.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/peregrine-falcon-cutting-pigeon-1055065289?src=b8FTrk5gDrMpiR9spDtjRw-1-43">shutterstock</a></span>
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<p>One slightly macabre alternative that occurs in big cities, involves <a href="http://jomec.co.uk/thecardiffian/2018/03/20/rspca-warning-two-birds-killed-queen-street/">the netting that often hangs around buildings</a>. Birds can easily fly into it and become entangled: not just old or sick pigeons, but any bird unfortunate enough not to notice it. Netting is usually high above the ground, so after some fruitless struggling dead pigeons usually hang there, away from the scavengers below. </p>
<p>Whether snatched midair by birds of prey, entangled by man made obstacles or alone in a remote corner of a skyscraper’s roof garden, there are many ways that pigeons pass on from this world. But they all take place within an internal urban ecosystem, that, for the most part, is hidden from our sight.</p><img src="https://counter.theconversation.com/content/98874/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Steve Portugal does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>London should be one giant pigeon cemetery, but you rarely see the bodies.Steve Portugal, Reader in Animal Biology and Physiology, Royal Holloway University of LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/813522017-07-21T10:25:04Z2017-07-21T10:25:04ZFive comic book superpowers that really exist in animals<figure><img src="https://images.theconversation.com/files/179160/original/file-20170721-18141-1ttgs9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Evolution has been occurring for billions of years, producing organisms that are perfectly adapted to their environments. And this includes abilities that we would normally consider superpowers if humans were to have them. But these powers really do exist in the animal kingdom.</p>
<h2>1. Echolocation</h2>
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<p>In the superhero world, Matt Murdock, who was blinded by radioactive waste as a child, developed a superhuman ability to sense using sound waves and became the superhero Daredevil. This gives Daredevil a 360-degree field of “vision”, allowing him to precisely locate objects or people in all directions, an obvious advantage over normal vision.</p>
<p>Bats, despite being nocturnal animals, cannot see in the dark. Instead they have evolved a similar ability known as use <a href="https://www.scientificamerican.com/article/how-do-bats-echolocate-an/">echolocation</a> to navigate and locate prey at night. The bat emits a very high frequency sound and listens for the echo that bounces off objects. The difference in time between emitting the sound and hearing the echo allows the bat to build up a mental “picture” of its environment. Sounds that take longer to bounce back indicate that the surroundings are further away. </p>
<p>Matt Murdock’s ability may not be too far from reality <a href="http://www.bbc.co.uk/news/magazine-19524962">as humans can also learn to use echolocation</a>. By making clicking noises or stomping their feet some visually impaired people are able to accurately “visualise” their surroundings. </p>
<h2>2. Magnetic Sense</h2>
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<p>The X-Men’s arch-villian Magneto can sense and manipulate magnetic fields with his mind. And some animals have a similar magnetic sense known as “magnetoreception” that they use to navigate and orient themselves. For example, homing pigeons are able to navigate back to their home lofts when visual cues are missing but can’t do so when magnets are nearby. This suggests that they may use the Earth’s <a href="http://www.pnas.org/content/68/1/102.full.pdf">magnetic field to navigate</a>. </p>
<p>Although we don’t understand exactly how they do this, pigeons have been found to possess a substance called magnetite in their beaks, which becomes magnetised when <a href="http://www.nature.com/news/2004/041122/full/news041122-7.html">exposed to magnetic fields</a>. So they may be following their nose, so to speak.</p>
<p>Of course, Magneto’s magnetic powers can produce a much wider range of effects, from lifting and manipulating metal objects to rearranging matter (a power definitely not seen in animals). However, his daughter Polaris has the ability to perceive the world as patterns of magnetic energy, which actually isn’t too dissimilar to the powers present in the animal kingdom.</p>
<h2>3. Shapeshifting</h2>
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<p>The ability to shapeshift and mimic the form of others is a formidable power for a superhero or villain – and has been used by X–Men’s Mystique on many occasions to lure and manipulate her foes. A rare few animals are capable of changing their shape and size in the real world, most notably <a href="http://theconversation.com/some-shape-shifting-animals-that-can-morph-to-fool-others-39616">the mimic octopus</a>.</p>
<p>It can alter its colour, behaviour, shape and texture to mimic a diverse range of species, with at least 13 examples <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8312.2007.00948.x/abstract">recorded so far</a> including sea snakes, jellyfish and sea anemones. Most of the impersonated species are poisonous, and so pretending to be them helps the octopus ward off predators. But this shapeshifter is also able to imitate its prey, possibly in an attempt to lure them in closer before feasting on them.</p>
<h2>4. Absorbing powers</h2>
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<p>The ability to steal the superpowers of another individual is surely the ultimate power, enabling you to have any power in existence. X–Men’s Rogue has the incredible ability to absorb superpowers of anyone she touches – but so do the Pitohui birds of New Guinea (well, almost). The feathers and skin of Pitohui contain a noxious substance, making them possibly the only poisonous birds in the world and giving them defence against predators. But the birds don’t appear to be able to produce the toxic substance directly. Instead, they acquire it by <a href="https://www.ncbi.nlm.nih.gov/pubmed/15520388">eating <em>Choresine</em> beetles</a>.</p>
<p>Furthermore, <a href="http://www.pnas.org/content/97/24/12970.full">scientists think</a> this toxicity might even rub off onto the birds’ eggs and young, making them toxic to predators as well, even though they have never eaten the <em>Choresine</em> beetles. So the infant birds are essentially absorbing the superpower from their parents in the same way that Rogue absorbs powers when she touches other people.</p>
<h2>5. Chemical weapons</h2>
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<p>One animal ability even goes beyond what has been imagined by superhero fiction. Bombardier beetles are noted for their unique defence mechanism that enables them to produce acid gas bombs to deter predators such as ants. In extreme cases they may bombard predators with a lethal dose of these chemical bombs that they kill them. <a href="http://www.pnas.org/content/96/17/9705.full">The acid bombs consist</a> of two chemical compounds stored separately in the beetle’s abdomen. When threatened, the beetles combine the two compounds, resulting in the production of a boiling mixture that explodes out of the tip of the directional abdomen as a gas.</p>
<p>You’d think this remarkable “weapon” was surely the precursor for a superpower. And the superheroes Anarchist and Zeitgeist (members of X Force) both have acid generation powers. Anarchist secretes an acid–like sweat, whereas Zeitgeist spews acidic vomit. But these are hardly formidable weapons. Perhaps it is time that some superheroes caught up with the amazing set of powers that have already evolved in the animal kingdom.</p>
<p><em>This article is an adapted extract from a chapter in “<a href="http://pubs.rsc.org/en/content/ebook/978-1-78262-487-5">The Secret Science of Superheroes</a>” published by the Royal Society of Chemistry.</em></p><img src="https://counter.theconversation.com/content/81352/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Louise Gentle works for Nottingham Trent University. She contributed to the Secret Science of Superheroes, published by the Royal Society of Chemistry, as an author. </span></em></p><p class="fine-print"><em><span>Mark Lorch is a member of the Royal Society of Chemistry. He contributed to the Secret Science of Superheroes, published by the Royal Society of Chemistry, as an author and editor. He has received funding from the Royal Society of Chemistry.</span></em></p>From shapeshifting octopi to acid-firing beetles.Louise Gentle, Senior Lecturer in Behavioural Ecology, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/794282017-07-13T04:11:54Z2017-07-13T04:11:54ZAre Australia’s native pigeons sitting ducks?<figure><img src="https://images.theconversation.com/files/174343/original/file-20170619-32085-pbtl7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">These migratory pied imperial-pigeons in Far North Queensland, like many of Australia's 22 species of native pigeons and doves, play an important role in our ecosystems but may be at risk from emerging viruses in domestic pigeons.</span> <span class="attribution"><span class="source">Dejan Stojanovic</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The word “pigeon” evokes thoughts of gentle cooing, fluttering in rafters, and poo-encrusted statues. The species responsible for the encrustation is deeply familiar to us, having ridden waves of European expansionism to inhabit every continent, including Australia. First domesticated thousands of years ago, urban pigeons have turned feral again. </p>
<p>Less familiar are the native species that are not your stereotypical pigeons: a posse of pointy-headed crested pigeons in a suburban park, or a flock of topknot pigeons feeding in a camphor laurel. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/174335/original/file-20170619-28805-116d2k5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/174335/original/file-20170619-28805-116d2k5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/174335/original/file-20170619-28805-116d2k5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=200&fit=crop&dpr=1 600w, https://images.theconversation.com/files/174335/original/file-20170619-28805-116d2k5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=200&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/174335/original/file-20170619-28805-116d2k5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=200&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/174335/original/file-20170619-28805-116d2k5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=251&fit=crop&dpr=1 754w, https://images.theconversation.com/files/174335/original/file-20170619-28805-116d2k5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=251&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/174335/original/file-20170619-28805-116d2k5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=251&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Crested pigeons (left), brush bronzewings (centre) and pied imperial-pigeons (right) are amongst the 22 species of native pigeons and doves in Australia. Their charm and beauty belies the important functions they play in ecosystems.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>Australia and its neighbouring islands are the global epicentre of pigeon and dove (or “columbid”) diversity with <a href="http://www.iucnredlist.org">the highest density of different columbids – an impressive 134 species – found in the region</a>. Twenty-two of these native species are found in Australia alone, <a href="http://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:08371787-659c-4546-b4db-b5d6b82eb391">in just about every habitat</a>. </p>
<p>These native species play an important role in ecosystem functioning: they forage for and disperse seeds, concentrate nutrients in the environment, and are a source of food for predators. Fruit doves for example, are zealous fruitarians, and <a href="http://onlinelibrary.wiley.com/doi/10.1002/9781444300321.ch16/summary">the region’s tropical rainforests depend on them for tree diversity</a>. Where <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2699.2002.00718.x/full">fruit-doves have disappeared in the South Pacific</a>, numerous plant species have lost an effective dispersal mechanism.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/174828/original/file-20170621-2627-vst3ab.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/174828/original/file-20170621-2627-vst3ab.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=638&fit=crop&dpr=1 600w, https://images.theconversation.com/files/174828/original/file-20170621-2627-vst3ab.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=638&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/174828/original/file-20170621-2627-vst3ab.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=638&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/174828/original/file-20170621-2627-vst3ab.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=801&fit=crop&dpr=1 754w, https://images.theconversation.com/files/174828/original/file-20170621-2627-vst3ab.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=801&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/174828/original/file-20170621-2627-vst3ab.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=801&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The rose-crowned fruit-dove is not only beautiful but also plays an important role in dispersing seeds in Australian rainforests.</span>
<span class="attribution"><span class="source">Author provided</span></span>
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<p>The future of Australia’s native pigeons however, may depend on our domestic pigeons. Australia’s domestic pigeon population — both feral and captive - is large and interconnected by frequent local and interstate movements. Pigeon racing, for example, involves releasing captive birds hundreds of kilometres from their homes only so they may find their way back. While most birds do navigate home, up to 20% will not return, <a href="http://www.sciencedirect.com/science/article/pii/S0960982211014588">of which some will join feral pigeon populations</a>. Birds are also <a href="http://agriculture.vic.gov.au/agriculture/livestock/interstate-livestock-movements">traded across the country</a> and <a href="http://www.abc.net.au/news/2012-11-17/exotic-bird-trade-going-unchecked/4376888">illegally from overseas</a>. These movements, together with poor biosecurity practices, mean that captive pigeons can and do mingle with feral domestic pigeons.</p>
<p>And here’s a paradox. Could Australia’s feral domestic pigeons become the vector for a dramatic decline of columbids – native species on which Australian ecosystems rely?</p>
<h2>Emerging viral epidemics</h2>
<p>In recent years, two notable infectious diseases have been found to affect our captive domestic pigeons: the <a href="http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0005/408146/Pigeon-paramyxovirus-PPMV1.pdf">pigeon paramyxovirus type 1</a> (PPMV1) and a new strain of the <a href="http://www.dpi.nsw.gov.au/animals-and-livestock/poultry-and-birds/health-disease/rotavirus-pigeon-disease/pigeon-rotavirus-communique-13-february-2017">pigeon rotavirus</a> (G18P). These diseases are notable because in captive domestic flocks they are both spectacularly lethal and difficult to control. </p>
<p>PPMV1, although likely to have <a href="https://invasives.org.au/wp-content/uploads/2014/09/sub74Rev_Att-2-ISC.pdf">originated overseas</a>, is now endemic in Australia. This virus has jumped from captive to feral domestic pigeon populations on several occasions, but fortunately has yet to establish in feral populations.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/174337/original/file-20170619-32085-fqk830.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/174337/original/file-20170619-32085-fqk830.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/174337/original/file-20170619-32085-fqk830.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/174337/original/file-20170619-32085-fqk830.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/174337/original/file-20170619-32085-fqk830.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/174337/original/file-20170619-32085-fqk830.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/174337/original/file-20170619-32085-fqk830.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/174337/original/file-20170619-32085-fqk830.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Domestic pigeons suffer high mortality rates after being infected with either pigeon paramyxovirus ‘PPMV1’ or pigeon rotavirus ‘G18P’.</span>
<span class="attribution"><span class="source">Dr Colin Walker</span></span>
</figcaption>
</figure>
<p>G18P is thought to have spread to Victoria and South Australia <a href="http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0004/698377/biosecurity-bulletin-rotavirus-pigeon-disease.pdf">from a bird auction in Perth in 2016</a>. PPMV1 also <a href="http://www.dpi.nsw.gov.au/animals-and-livestock/poultry-and-birds/health-disease/advice-for-bird-owners">spread rapidly to multiple states following its first appearance in Melbourne in 2011</a>.</p>
<p>The movements of captive pigeons, and their contact with their feral counterparts, can be the route through which virulent and lethal diseases – such as the PPMV1 and the G18P – may spread to Australia’s native columbids.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/174650/original/file-20170620-24871-11xeq9v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/174650/original/file-20170620-24871-11xeq9v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/174650/original/file-20170620-24871-11xeq9v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=301&fit=crop&dpr=1 600w, https://images.theconversation.com/files/174650/original/file-20170620-24871-11xeq9v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=301&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/174650/original/file-20170620-24871-11xeq9v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=301&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/174650/original/file-20170620-24871-11xeq9v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=378&fit=crop&dpr=1 754w, https://images.theconversation.com/files/174650/original/file-20170620-24871-11xeq9v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=378&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/174650/original/file-20170620-24871-11xeq9v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=378&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pigeon paramyxovirus and pigeon rotavirus are known to have escaped from captive domestic pigeons into feral domestic pigeons (black arrow). The risk is that these viruses will establish in feral pigeon populations and cause epidemics in our diverse and ecologically important wild native columbids (red arrow).</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>What have we got to lose?</h2>
<p>Fortunately, neither PPMV1 nor G18P has crossed over to Australia’s native columbids. We can’t say how likely this is, or how serious the consequences would be, because we have not previously observed such viral infections among our native pigeons. </p>
<p>If the viruses prove equally lethal to native columbids as they are to domestic pigeons, we could see catastrophic population declines across numerous columbid species in Australia over a short period of time.</p>
<p>Should these viruses spread (via feral domestic pigeons), the control and containment of losses among our native pigeon species would be near impossible. Such a nightmare scenario can only be avoided by predicting if and how these viruses might “spill over” into wild columbids so that we can prevent this in the first place.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/174339/original/file-20170619-28797-1ae82id.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/174339/original/file-20170619-28797-1ae82id.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/174339/original/file-20170619-28797-1ae82id.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=240&fit=crop&dpr=1 600w, https://images.theconversation.com/files/174339/original/file-20170619-28797-1ae82id.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=240&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/174339/original/file-20170619-28797-1ae82id.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=240&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/174339/original/file-20170619-28797-1ae82id.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=302&fit=crop&dpr=1 754w, https://images.theconversation.com/files/174339/original/file-20170619-28797-1ae82id.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=302&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/174339/original/file-20170619-28797-1ae82id.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=302&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Maps of Australia showing the overlapping distribution of our 22 native pigeon and dove species (left) and the distribution (in orange) and verified individual records (red dots) of introduced feral domestic pigeons (right).</span>
<span class="attribution"><span class="source">Atlas of Living Australia, Birdlife International</span></span>
</figcaption>
</figure>
<h2>Protecting our pigeons</h2>
<p>Agricultural poultry is routinely screened to check their vulnerability to threats like the PPMV1 and G18P. Such screening is an appropriate response to protect our agricultural industry. </p>
<p>For our native pigeons and doves however, no such similar testing is planned. Based on progress in <a href="http://www.sciencedirect.com/science/article/pii/S0168170211000414">veterinary vaccine development</a> and <a href="https://www.ala-schweiz.ch/images/stories/pdf/ob/2003_100/OrnitholBeob_2003_100_33_Haag-Wackernagel.pdf">advancements in understanding of feral pigeon control</a>, the knowledge and technology required to mitigate this threat should be relatively inexpensive. The threat for these species can be actively managed, now, by improving our biosecurity and vaccination programs for captive domestic pigeons, and eradicating feral domestic pigeons. </p>
<p>The protection of our native columbids however, ultimately relies on valuing their ecosystem functions in the first place.</p><img src="https://counter.theconversation.com/content/79428/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Peters works for Charles Sturt University. He has received funding from the former Wildlife Exotic Disease Preparedness Program, Department of Agriculture, Fisheries and Forestry. He is affiliated with the Wildlife Disease Association and Wildlife Health Australia. </span></em></p>Two recently emerging viruses in domestic pigeons in Australia may pose a significant threat to Australia’s 22 species of native pigeons and doves, many of which have crucial ecosystem roles.Andrew Peters, Senior Lecturer in Veterinary Pathology, Charles Sturt UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/563152016-03-17T11:45:59Z2016-03-17T11:45:59ZPigeon Air Patrol: a realistic way of monitoring pollution or cooing over unproved science?<figure><img src="https://images.theconversation.com/files/115295/original/image-20160316-30211-unsm9z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">These backpacked pigeons are patrolling London's skies.</span> <span class="attribution"><span class="source">Pigeon Air Patrol</span></span></figcaption></figure><p>A novel way of monitoring air pollution in London has taken flight. The <a href="http://www.pigeonairpatrol.com/">Pigeon Air Patrol</a> has set loose a <a href="http://www.theguardian.com/environment/2016/mar/14/pigeon-patrol-takes-flight-to-tackle-londons-air-pollution-crisis">legion of winged “scientists”</a>, complete with small backpacks containing sensors that measure levels of nitrogen dioxide, and several other pollutants.</p>
<p>This is just the latest in a range of high-profile citizen science projects that use small, low-cost air quality sensors (not all of which are strapped to pigeons). If the media hype is to be believed, <a href="http://www.economist.com/news/science-and-technology/21692848-tackling-atmospheric-pollution-hard-more-data-will-help-something-air">start-up companies from London to San Francisco are now using these sensors</a> to provide detailed information on air pollution levels where people actually live and work. </p>
<p>The ambition is to create a democratisation in information, better informing the public and enabling lifestyle decisions that limit their exposure – and creating data that pressures local authorities to clean up the air its residents breathe.</p>
<p>This is big news when you consider that in the UK alone air quality is estimated to be responsible for <a href="http://www.bbc.co.uk/news/health-35629034">over 30,000 premature deaths a year</a>. </p>
<p>The UK government currently invests significant money into <a href="http://uk-air.defra.gov.uk/networks/">measuring real-time air pollution</a> at around 150 air quality monitoring sites, where highly trained personnel operate expensive, high-tech instruments. The costs run to many millions of pounds a year – but why bother when a flock of pigeons could provide a much higher density of measurements for a fraction of the price? </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"709320860226740224"}"></div></p>
<p>Atmospheric scientists love their gadgets and invest significant time and money in developing and running equipment to measure the chemical composition of the atmosphere. Yet very few have embraced this apparent sensor revolution – and even fewer have published data on them in scientific literature. </p>
<p>Despite the user-friendly apps, clever websites and considerable media publicity with crowd-sourced funding, virtually none of this new monitoring tech – pigeon-borne or otherwise – has supporting evidence that it can provide accurate measurements in the real atmosphere. The assumption being that it must be – and very few people have any way of checking for themselves.</p>
<h2>Flights of fancy</h2>
<p>We have spent the past 12 months at the Wolfson Atmospheric Chemistry Laboratories looking into just <a href="http://pubs.rsc.org/en/Content/ArticleLanding/2015/FD/C5FD00201J#!divAbstract">how well these low-cost air monitoring sensors perform</a>, with an interesting result: when relying on data from these sensors you must be very cautious indeed.</p>
<p>We exposed different sensors to a wide range of chemicals and conditions that they would encounter in the real world, and compared the data with more established technologies. The majority of sensors tested did indeed respond to the chemicals they are designed to measure and, after calibration, could measure realistic ambient concentrations in short, controlled laboratory experiments. But we also found that many of the sensors also responded to a whole range of other pollutants and that responses from these chemicals could swamp the device and give artificial readings. </p>
<p>We also saw large sensor-to-sensor variability: 20 identical commercial air quality sensor units running side by side for two weeks reported pollution numbers that differed by up to a factor of ten.</p>
<p>Overall, our results found that the quality of the data fed back by some low-cost sensors can be misleading – often reporting pollution to be worse than it actually was – and, in some cases, completely wrong.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"709495536571817984"}"></div></p>
<p>As an atmospheric chemist, whose career has been spent building and testing instruments to measure chemicals in the atmosphere, the results from these experiments were no great surprise. Our atmosphere is an incredibly complex mixture and the concentrations of pollutants are actually very low. For example, the current <a href="http://ec.europa.eu/environment/air/quality/standards.htm">EU air quality guideline</a> for nitrogen dioxide is about 20 molecules in every billion. </p>
<p>Atmospheric measurement technology is constantly improving and miniaturising, but over the decades improvements have been gradual and incremental. In my opinion, this new approach in air pollution sensors is simply trying to leap too big a gap in one go.</p>
<p>Are these just the complaints of an elitist scientist, moaning about the public getting in on our research area? Perhaps these sensors are just a bit of fun? It all depends of course on how the data are used. If the aim is to simply engage public interest in the issues, then perhaps the quality of data doesn’t matter. But what if an asthma sufferer makes medication decisions based on the read-outs of their local sensor? </p>
<p>If the road outside your house was closed because of a high pollution warning from a sensor, you would want this to be based on the most accurate data available. In many developing countries <a href="http://www.economistinsights.com/sustainability-resources/opinion/something-air">low-cost sensors are being installed</a> to manage often-chronic air pollution problems in place of more expensive traditional monitors. Should policy and investment in these places be based on technologies without acknowledging their weaknesses as well as their strengths? Even the UN Environment Programme <a href="http://www.unep.org/NewsCentre/default.aspx?DocumentID=26840&ArticleID=35403">has promoted a low-cost pollution sensor</a>, but has never published real-world data that demonstrates the sensors work in this application.</p>
<p>If we can cut through the hype, there really is fantastic potential for sensor systems in understanding human exposure, managing emissions and supporting effective policy. Undoubtedly these sensors work to some degree but, like all measurement science, the hard yards need to be done in the lab first in order to understand how this technology performs in the complex mixture that is our atmosphere. Less emphasis on websites and apps and rather more on characterisation and calibration will ultimately help solve some of these problems.</p><img src="https://counter.theconversation.com/content/56315/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Pete Edwards receives funding from the European Commission (Marie Skłodowska-Curie actions) to research potential applications for sensor technology in atmospheric science. </span></em></p>This low-cost way of monitoring air quality is appealing, but there needs to be acknowledgement of their weaknesses as well as strengths.Pete Edwards, Marie Curie research fellow, University of YorkLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/256332014-04-23T05:20:01Z2014-04-23T05:20:01ZExplainer: how do homing pigeons navigate?<figure><img src="https://images.theconversation.com/files/46567/original/yzc3wcp9-1397652010.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Not stopping for directions.</span> <span class="attribution"><a class="source" href="http://en.wikipedia.org/wiki/File:Rock_dove_-_natures_pics.jpg">Alan D. Wilson</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Pigeons have extraordinary navigational abilities. Take a pigeon from its loft and let it go somewhere it has never been before and it will, after circling in the sky for while, head home. This remarkable capacity extends to places tens even hundreds of kilometres from its home and is all the more remarkable to humans because we are apparently incapable of it ourselves. </p>
<p>But we have long made use of the pigeon’s homing ability, principally for carrying messages in the past. And for several decades now the pigeon has played centre stage in scientists’ attempts to understand the map and compass mechanisms fundamental to bird navigation.</p>
<h2>So what have we learnt?</h2>
<p>Out of direct contact with home, and out of the landscape to which birds have become familiar, there must nonetheless be large-scale cues available to the navigating bird with which it can estimate its position relative to home. Many theories have waxed and waned, from reading the <a href="http://www.sciencemag.org/content/291/5502/300">sun’s arc</a> to the detection of <a href="http://link.springer.com/article/10.1007/BF00679906">long-distance infra-sounds</a>. But there is little support for these.</p>
<h2>Magnetic misgivings</h2>
<p>Most attractive and persistent has been the idea that pigeons can use the predictable gradients of intensity and dip-angle in the <a href="http://news.bbc.co.uk/1/hi/sci/tech/4038179.stm">earth’s magnetic field</a> to map their position relative to known values at home. The magnetic map hypothesis is attractive and persistent, but largely without support after decades of experimental research. It is also <a href="http://www.springer.com/life+sciences/behavioural/book/978-3-540-22385-6">probably false</a>. </p>
<p>Part of the confusion is that many birds (and probably pigeons) do have a magnetic compass which gives them a sense of direction when they cannot see the sun. A compass helps make long-distance movement efficient and is central to migration, but it cannot help you navigate if you do not know the direction of your goal. This requires a map. Unlikely as it may seem, this map turns out almost certainly to be olfactory – pigeons, and perhaps all birds, navigate using smell.</p>
<h2>Good nose for direction</h2>
<p>Pigeons deprived of the ability to smell cannot navigate. Fool them with air form the wrong site and they will fly in the wrong direction. This sounds a simple thing to demonstrate, but in fact testing the olfactory navigation hypothesis conclusively has proved remarkably taxing and there are still experts who doubt it on reasonable grounds. </p>
<p>But the <a href="http://jeb.biologists.org/content/216/12/2165.short">weight of evidence</a> from 40 years of study makes the case pretty strong. It’s likely that birds learn the rough composition of atmospheric volatiles characteristic of their home area and how this varies with winds that come from different directions, and are then able to extrapolate to unfamiliar places if they are blown off-course or taken there by a human and released. Even <a href="http://jeb.biologists.org/content/216/15/2798.abstract">over the open oceans</a>, birds (not pigeons of course) may use odours to navigate.</p>
<p>Closer to home, however, olfactory deprivation has little effect on a pigeon’s orientation, and it seems that they switch to a second mechanism dominated by visual landscape cues. Until recently scientists lacked the tools to observe detailed movement with sufficient detail outside the laboratory. But the advent of miniature on-board tracking technologies such as GPS now allows us to follow birds with astonishing precision and unravel the mechanisms of their spatial cognition in the wild.</p>
<h2>New findings</h2>
<p>We’ve now learn that pigeons repeatedly released from the same site soon learn a habitual route home which they stick to faithfully even if it is <a href="https://doi.org/10.1242/jeb.092908">not the quickest</a>. Different individuals learn, and stick to, different routes. Routes often follow linear landscape features, such as roads or field margins, but are learnt most effectively over landscapes of intermediate complexity. This means that urban landscapes <a href="http://rsbl.royalsocietypublishing.org/content/10/1/20130885.full">may in fact be too complex</a> for optimum route learning. </p>
<p>Pair birds with different ideas about how to get home from the same place and the result is an elegant exposé of each bird’s <a href="http://bit.ly/1myqmDW">propensity to lead out or follow others</a>. Birds that are more faithful to their own route when homing alone are <a href="http://rsbl.royalsocietypublishing.org/content/7/1/63">more likely to emerge as leaders</a> when homing socially.</p>
<p>So if the pigeon’s brain contains a network of learnt routes, how are these memories acquired and how do they interact? Recently, my colleagues Andrea Flack and Dora Biro <a href="http://dx.doi.org/10.1098/rsbl.2014.0119">showed</a> that having to learn three routes in parallel doesn’t cause pigeons any additional confusion. Route-learning is memorised independently, regardless of whether the sites they are released from are encountered sequentially, randomly intermingled or in strict rotation. </p>
<p>Treating the art of pigeon homing as a natural learning laboratory is a new science into which we are just taking the first steps, and it seems that we have yet to find the boundaries of the bird’s abilities. Clearly, we still have much to learn from the pigeon.</p><img src="https://counter.theconversation.com/content/25633/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tim Guilford has received funding from EPSRC, BBSRC, NERC, RSPB, John Fell, Merton College.</span></em></p>Pigeons have extraordinary navigational abilities. Take a pigeon from its loft and let it go somewhere it has never been before and it will, after circling in the sky for while, head home. This remarkable…Tim Guilford, Professor of Animal Behaviour, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/48832012-02-29T19:47:16Z2012-02-29T19:47:16ZPigeons can count, but chicks are even better<figure><img src="https://images.theconversation.com/files/8154/original/9b43ztpw-1330401682.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cute, cuddly and numerically competent.</span> <span class="attribution"><span class="source">timsackton</span></span></figcaption></figure><p>The humble pigeon has been in the scientific spotlight lately since the discovery that the much-maligned species is far smarter than previously thought. A study by psychologist Damian Scarf and colleagues – <a href="https://theconversation.com/are-pigeons-as-smart-as-primates-you-can-count-on-it-4904">discussed recently on The Conversation</a> – showed pigeons possess numerical abilities comparable to those found in primates.</p>
<p>But while pigeons surprised many with their “numerical competence”, there’s arguably an even better performer among our feathered friends: the domestic chick (<em>Gallus gallus</em>).</p>
<p>More on chicks in a moment, of course, but before we get there it’s worth asking: why all the buzz about the numerical ability of animals?</p>
<p>This area has attracted particular interest in the past few decades because numerical competency has, traditionally, been linked with language. Put simply, it was long believed that numerical competency evolved in humans at the same time as language.</p>
<p>We now know this to be untrue. To explain why, we need to understand the <a href="http://www.nature.com/nrn/journal/v6/n3/abs/nrn1626.html">different levels of numerical ability</a>.</p>
<p>The most basic form is the ability to make judgments of size between different sets of items (“there are three worms in this group and four in that group”). This ability serves animals well in food searching and allows such animals to choose collections of food with more items. This ability is demonstrated by very young domestic chicks when they choose to approach objects on which they have been <a href="http://www.columbia.edu/cu/psychology/terrace/w1001/readings/hess.pdf">imprinted</a>.</p>
<p>Italian psychologists Rosa Rugani, Lucia Regolin and (one of your current authors) Giorgio Vallortigara <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1467-7687.2009.00936.x/abstract">showed chicks prefer to join groups of more objects</a> versus a single object or a smaller set of objects. Since these “objects” would normally be social companions, the preference for larger groups probably reflects flocking behaviour.</p>
<p>The results of these tests, made with many adequate controls, were quite similar to those obtained with <a href="http://www.education.com/magazine/article/babies-know-numbers/">human infants</a>. Human infants, it would seem, are also attracted to larger groups.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/8155/original/3gjjbdc3-1330401932.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/8155/original/3gjjbdc3-1330401932.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/8155/original/3gjjbdc3-1330401932.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/8155/original/3gjjbdc3-1330401932.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/8155/original/3gjjbdc3-1330401932.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/8155/original/3gjjbdc3-1330401932.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/8155/original/3gjjbdc3-1330401932.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">HerbertT/Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>The next numerical ability is recognition of “serial relations” (the order of numbers), as seen in monkeys and in the pigeons studied by Scarf and colleagues. Simply put, monkeys and pigeons can be trained to discriminate between the numbers one to nine in ascending order and can do so with relative ease or difficulty according to <a href="http://www.britannica.com/EBchecked/topic/638610/Webers-law">Weber’s Law</a>.</p>
<p>Weber’s Law states that the difficulty of any numerical discrimination depends on the ratio of the two numbers. For instance, animals trained to discriminate between the numbers three and four can also discriminate with ease between six and eight (being two times three and four, respectively) but find discrimination between three and five more difficult.</p>
<p>As discussed by Scarf and colleagues in their paper, monkeys and pigeons demonstrate an ability to learn to choose a target on the basis of its ordinal position (for example, third, eighth, ninth) in an array.</p>
<p>Pigeons (and monkeys) are not special in having this ability. Rats and bees have the ability to recognise ordinal position and, as seen in <a href="https://docs.google.com/presentation/d/1dFYp6M4pHWgpZ6OrVVOFUTA7JyDlrPf4PfY3TWFLwZk/edit">the experiments by Rugani, myself (Giorgio) and colleagues</a>, young chicks possess this ability too.</p>
<p>The most complex numerical ability is to manipulate numbers by performing simple arithmetic. We know rhesus monkeys can do this and we know that five-day-old chicks can too.</p>
<p>My colleagues and I (Giorgio) <a href="http://rspb.royalsocietypublishing.org/content/276/1666/2451">imprinted chicks on a small ball</a> and then allowed them to watch as the imprinting ball moved behind one of two screens in a large arena.</p>
<p>After being released into the testing arena, the chicks approach the screen behind which they had seen the ball disappear. Since chicks prefer to approach a group of imprinting objects, rather than one or a group of fewer objects, this test can be used to determine whether they can add and subtract.</p>
<p>Several balls can be made to disappear behind one screen and then re-appear to move behind the other screen as the chick watches. Once released into the arena, the chick chooses the screen behind which more balls have disappeared in the final step of the test. In other words, the chick has been able to subtract balls that move from one screen to the other and add to those it has already seen disappear behind a screen (see video below).</p>
<p>This ability is more complex than that demonstrated in the pigeon.</p>
<figure>
<iframe src="https://player.vimeo.com/video/37569633" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
</figure>
<p>The experiments used to show this in chicks do not require excessive training, while the pigeons tested by Scarf and colleagues did. Excessive training can cause problems of its own but, most importantly, the numerical abilities shown by young chicks suggest animals possess core systems of knowledge about numerosity, just as they also do about geometry and the physical properties of objects.</p>
<p>So what does all of this mean?</p>
<p>Well, it shows that numerical competence evolved early and that, in the evolution of animals (including humans), numerical competence appeared long before language did. Of course it also means there’s far more to chicks than just cute balls of fluff.</p>
<p><strong>Further reading:</strong></p>
<ul>
<li><a href="https://docs.google.com/presentation/d/1dFYp6M4pHWgpZ6OrVVOFUTA7JyDlrPf4PfY3TWFLwZk/edit">Numerical competency in newborn chicks</a></li>
</ul><img src="https://counter.theconversation.com/content/4883/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The humble pigeon has been in the scientific spotlight lately since the discovery that the much-maligned species is far smarter than previously thought. A study by psychologist Damian Scarf and colleagues…Lesley Rogers, Emeritus Professor of Neuroscience, University of New EnglandGiorgio Vallortigara, Professor of Cognitive Neuroscience, University of TrentoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/49042012-01-11T19:27:58Z2012-01-11T19:27:58ZAre pigeons as smart as primates? You can count on it<figure><img src="https://images.theconversation.com/files/6873/original/jrff7z83-1326252442.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The humble pigeon mightn't look smart, but it's no bird-brain.</span> <span class="attribution"><span class="source">Seamoor</span></span></figcaption></figure><p>We humans have long been interested in defining the abilities that set us apart from other species. Along with capabilities such as language, the ability to recognise and manipulate numbers (“numerical competence”) has long been seen as a hallmark of human cognition.</p>
<p>In reality, a number of animal species are numerically competent and according to <a href="http://www.sciencemag.org/content/334/6063/1664">new research</a> from <a href="http://www.otago.ac.nz/news/news/otago029568.html">psychologists at the University of Otago</a> in New Zealand, the humble pigeon could be one such species.</p>
<p>Damian Scarf, Harlene Hayne and Michael Colombo found that pigeons possess far greater numerical abilities than was previously thought, actually putting them on par with primates.</p>
<p>More on pigeons in a moment, but first: why would non-human animals even need to be numerically competent? Would they encounter numerical problems in day-to-day life?</p>
<p>In fact, there are many reports indicating that number is an important factor in the way many species behave.</p>
<p><a href="http://www.wbu.com/chipperwoods/photos/cowbird.htm">Brown cowbirds</a> are nest parasites – they lay their eggs in the nests of “host” species; species that are then landed with the job of raising a young cowbird.</p>
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<img alt="" src="https://images.theconversation.com/files/6871/original/9chngfcg-1326252024.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/6871/original/9chngfcg-1326252024.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/6871/original/9chngfcg-1326252024.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/6871/original/9chngfcg-1326252024.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/6871/original/9chngfcg-1326252024.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/6871/original/9chngfcg-1326252024.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/6871/original/9chngfcg-1326252024.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><span class="source">Sir_Iwan</span></span>
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<p>Cowbirds are sensitive to the number of eggs in the host nest, <a href="http://www.mendeley.com/research/counting-chicks-before-they-hatch-female-cowbirds-can-time-readiness-of-a-host-nest-for-parasitism/">preferring to lay in nests with three host eggs</a> rather than one. This presumably ensures the host parent is close to the end of laying a complete clutch and will begin incubating shortly after the parasite egg has been added.</p>
<p>Crows identify individuals by the number of caw sounds in their vocalisations, while lionesses appear to evaluate the risk of approaching intruder lions based on <a href="http://www.cbs.umn.edu/lionresearch/publications/articles/Roaring_and_numerical_assessment_in_contests_between_groups_of_female_lions.pdf">how many individuals they hear roaring</a>.</p>
<p>But numerical competence is about more than an ability to count. In fact, it’s <a href="http://www.nature.com/nrn/journal/v6/n3/abs/nrn1626.html">three distinct abilities</a>:</p>
<ul>
<li><strong>the “cardinal” aspect</strong>: the ability to evaluate quantity (eg. counting the number of eggs already in a nest)</li>
<li><strong>the “ordinal” aspect</strong>: the ability to put an arbitrary collection of items in their correct order or rank (eg. ordering a list of animals based on the number of legs they have, or ordering the letters of the alphabet)</li>
<li><strong>the “symbolic” aspect</strong>: the ability to symbolically represent a given numerical quantity (eg. the number “3” or the word “three” are symbols that represent the quantity 3).</li>
</ul>
<p>We know that humans are capable of all three aspects of numerical competence, but what about other animals?</p>
<p>For a start, we already know that the cowbird, lion and crow possess the cardinal aspect of numerical competency – they are all able to count. Pigeons possess the cardinal aspect too (as was reported <a href="http://www.mendeley.com/research/vom-erlernen-unbenannter-anzahlen-bei-vgeln-learning-unnamed-amounts-birds/">as early as 1941</a>) as do several other vertebrate and invertebrate species.</p>
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<img alt="" src="https://images.theconversation.com/files/6870/original/rd3gfcfq-1326251705.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/6870/original/rd3gfcfq-1326251705.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=430&fit=crop&dpr=1 600w, https://images.theconversation.com/files/6870/original/rd3gfcfq-1326251705.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=430&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/6870/original/rd3gfcfq-1326251705.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=430&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/6870/original/rd3gfcfq-1326251705.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=540&fit=crop&dpr=1 754w, https://images.theconversation.com/files/6870/original/rd3gfcfq-1326251705.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=540&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/6870/original/rd3gfcfq-1326251705.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=540&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
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<span class="attribution"><span class="source">HarlanH</span></span>
</figcaption>
</figure>
<p>And in 1998, Elizabeth Brannon and Herbert Terrace <a href="http://www.sciencemag.org/content/282/5389/746.abstract">showed</a> that <a href="http://en.wikipedia.org/wiki/Rhesus_macaque">rhesus monkeys</a> have the ability to order arrays of objects according to the number of items contained within these arrays. After learning to order sets of one, two and three items, the monkeys were able to order any three sets containing from one to nine items. </p>
<p>This discovery represented a clear progression in complexity, since ranking according to numerical quantity is an abstract ability – the ordinal aspect.</p>
<p>The new research by Scarf, Hayne and Colombo – which was published in Science in late December – has pushed, even further, our understanding of numerical abilities in the animal kingdom.</p>
<p>So what did they do?</p>
<p>Well, first they trained pigeons to peck three “stimulus arrays” – collections of objects on a touch screen. These arrays contained one, two or three objects and to receive a reward, the pigeon had to peck the arrays in order – the array with one object first, the array with two objects second, the array with three objects third.</p>
<p>Once this basic requirement was learned, the pigeons were presented with different object sets – one set containing arrays with one to three objects, and sets containing up to nine objects. </p>
<p>Having been presented with these novel object sets, the pigeons were once again required to peck the sets in ascending order. Pigeons solved the task successfully, even though they had never been trained with arrays containing more than three items.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/6869/original/tdsf28rq-1326248566.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/6869/original/tdsf28rq-1326248566.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=842&fit=crop&dpr=1 600w, https://images.theconversation.com/files/6869/original/tdsf28rq-1326248566.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=842&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/6869/original/tdsf28rq-1326248566.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=842&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/6869/original/tdsf28rq-1326248566.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1058&fit=crop&dpr=1 754w, https://images.theconversation.com/files/6869/original/tdsf28rq-1326248566.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1058&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/6869/original/tdsf28rq-1326248566.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1058&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A pigeon taking part in the University of Otago experiment.</span>
<span class="attribution"><span class="source">William van der Vliet</span></span>
</figcaption>
</figure>
<p>In fact, they performed on par with rhesus monkeys, demonstrating that both pigeons and monkeys are able to identify and order the numbers from one to nine. This is significant because it shows these complex numerical abilities are not confined to the primates (and that pigeons are smarter than many people think!)</p>
<p>So if non-human animals possess the cardinal and ordinal aspects of numerical competency, that means it’s the symbolic representation of numbers that makes humans unique, right?</p>
<p>As it turns out, no.</p>
<p>It’s <a href="http://www.reznikova.net/reznikova_ryabko_Behaviour_April-011.pdf">been shown</a> that <a href="http://en.wikipedia.org/wiki/Formica_polyctena">red wood ants (<em>Formica polyctena</em>)</a> can not only count up to several tens (20, 30 etc.), but can also communicate this numerical information to their brethren. </p>
<p>It would seem, therefore, that not even the symbolic representation of numerical information is specific to humans.</p>
<p>Of course, we still have much more to discover and understand within this fascinating field of research. In the meantime, you might want to think twice before dismissing pigeons as “stupid birds”.</p><img src="https://counter.theconversation.com/content/4904/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>We humans have long been interested in defining the abilities that set us apart from other species. Along with capabilities such as language, the ability to recognise and manipulate numbers (“numerical…David Guez, Lecturer, School of Psychology, University of NewcastleAndrea S. Griffin, Lecturer, School of Psychology, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.