tag:theconversation.com,2011:/global/topics/feathers-26604/articlesFeathers – The Conversation2023-01-11T18:33:01Ztag:theconversation.com,2011:article/1934332023-01-11T18:33:01Z2023-01-11T18:33:01ZPenguin feathers help inspire new de-icing techniques<figure><img src="https://images.theconversation.com/files/503369/original/file-20230106-23-k7ud43.jpg?ixlib=rb-1.1.0&rect=142%2C179%2C3996%2C2146&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The perpetually ice-free Gentoo penguin can serve as inspiration for the creation of passive anti-icing surfaces.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/38007185@N00/8466304187/">(ravas51/flickr)</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/penguin-feathers-help-inspire-new-de-icing-techniques" width="100%" height="400"></iframe>
<p>Walking down a road during a white winter comes with its own set of challenges: the frigid cold, stepping around slippery ice on roads and the need to switch sidewalks to avoid <a href="https://montreal.ctvnews.ca/icicles-are-daggers-and-they-drop-expert-says-dangerous-icicles-can-also-point-to-problems-in-your-house-1.5316121?cache=%3FclipId%3D1745623">dagger-sharp icicles that could potentially fall from above</a>. </p>
<p>This accumulated ice on roofs and rain gutter overhangs is not merely an annoyance and danger, but also requires tremendous efforts to remove. Standard ice removal techniques rely on <a href="https://doi.org/10.1038/s41467-022-32852-6">mechanical, thermal or chemical action</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/503367/original/file-20230106-22-mq16ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An airplane is sprayed with deicing fluid" src="https://images.theconversation.com/files/503367/original/file-20230106-22-mq16ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/503367/original/file-20230106-22-mq16ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=352&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503367/original/file-20230106-22-mq16ci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=352&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503367/original/file-20230106-22-mq16ci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=352&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503367/original/file-20230106-22-mq16ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=442&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503367/original/file-20230106-22-mq16ci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=442&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503367/original/file-20230106-22-mq16ci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=442&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An airplane is sprayed with de-icing fluid to prevent the formation of ice before take-off.</span>
<span class="attribution"><span class="source">(AP Photo/David Zalubowski)</span></span>
</figcaption>
</figure>
<p>The ice on road signs, electrical transmission pylons and cables is removed by hitting the ice slabs to induce vibrations to the object or by bending the structure. </p>
<p><a href="http://www.cnn.com/2010/TRAVEL/12/22/airplane.deicing/index.html">Airplanes are sprayed with de-icing fluids</a> that chemically melt and prevent the formation of ice before take-off. And like <a href="https://www.cbsnews.com/chicago/news/no-shoveling-salting-needed-as-heated-sidewalks-in-oak-park-melts-snow-upon-contact/">heated sidewalks</a>, airplane wings are typically heated in flight to melt ice that can form on their leading edges. </p>
<p>While all these anti-icing approaches are necessary to avoid fatal infrastructure failure and accidents, these techniques are unsustainable as they require tremendous amounts of <a href="https://www.nbcnews.com/id/wbna33071411">energy and harmful chemicals</a>. Over the past few decades, <a href="https://doi.org/10.1126/science.aba5010">researchers have tried to</a> develop passive anti-icing technology — a surface that would not allow ice to form on it or would require very little effort to dislodge any small inconsequential pieces of ice that did.</p>
<p>Our team of researchers at McGill University’s <a href="http://kietzig-lab.mcgill.ca/">Biomimetic Surface Engineering Laboratory</a> looked to nature for these solutions. Nature takes a different approach to solving its icy surface problems. Through millennia, species have adapted to possess an array of surface functions that do not require harsh chemistry or huge amounts of energy input. We found the <a href="https://doi.org/10.1021/acsami.2c16972">solution to de-icing challenges in the feathers of adorable wobble-gaited penguins</a>.</p>
<h2>Reading between the feathers</h2>
<p>When we set out to develop a passive anti-icing surface last winter, we thought about how penguins have never been photographed with a big ice crust on their plumage, despite living in really cold environments, swimming and hunting in frigid waters and standing in high winds. </p>
<p>We contacted the <a href="https://espacepourlavie.ca/en/biodome">Montréal Biodome</a> — which showcases different ecosystems — and visited their <a href="https://espacepourlavie.ca/en/biodome-fauna/gentoo-penguin">sub-Antarctic exhibit with Gentoo penguins</a>. They also gave us a jar full of shed Gentoo feathers. </p>
<p>We studied the microstructure and <a href="https://doi.org/10.1098/rsif.2014.0287">wetting behaviour</a> of individual feathers and also reassembled them into a feather mat to study whether or not they attract ice. Wetting behaviour characterizes how water droplets behave on the surface. Basically, it checks whether droplets roll off like tiny soccer balls or spread out in a puddle or whether the outcome is something in between.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/503363/original/file-20230106-17-bvp86r.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Penguin feather photograph" src="https://images.theconversation.com/files/503363/original/file-20230106-17-bvp86r.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503363/original/file-20230106-17-bvp86r.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=352&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503363/original/file-20230106-17-bvp86r.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=352&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503363/original/file-20230106-17-bvp86r.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=352&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503363/original/file-20230106-17-bvp86r.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=442&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503363/original/file-20230106-17-bvp86r.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=442&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503363/original/file-20230106-17-bvp86r.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=442&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 Gentoo penguin feather (left) alongside an image of its microstructure. Wire-like barbs, and barbules branch off the feather’s central stem.</span>
<span class="attribution"><span class="source">(Michael Wood)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our analysis showed that the <a href="https://www.mcgill.ca/iwais2022/files/iwais2022/paperid084.pdf">penguin’s plumage has both water-shedding and ice-shedding properties</a>. The preening oil that the bird applies when it grooms itself did not appear to play a role in ice-shedding. This led us to suspect that these effects come from the structure of its feathers, which meant that the structure of penguin feathers could provide a radically different approach to creating surface designs with passive anti-icing properties.</p>
<p>The detailed features of every individual feather and the role of the hamuli — a part of the feather that hooks individual feathers together into a mat — inspired us to replicate this natural wire-like mesh of a structure using woven textiles.</p>
<p>In order to mimic the microstructure of the penguin feathers we observed, we selected <a href="https://doi.org/10.1021/acsami.2c16972">stainless steel cloths with wire diameters and pore sizes</a> similar to those of the feathers. We also used our ultrafast laser processing equipment to match the longitudinal nano-sized grooves seen on the barbs and barbules of the penguin feather’s structure.</p>
<h2>Creating water- and ice- repelling surfaces</h2>
<p>Our research found that while a water-repellent surface is a definite requirement for stainless steel mesh cloth to shed water, this requirement becomes less important as the temperature decreases. </p>
<p>This is because water actually penetrates the previously empty mesh pores and freezes slowly as the temperatures drop low, creating cracks in the ice surface. This means that the surface can easily repel water and ice at freezing temperatures.</p>
<figure class="align-center ">
<img alt="A Gentoo penguin walks on snow" src="https://images.theconversation.com/files/492383/original/file-20221028-67386-5tqk25.jpg?ixlib=rb-1.1.0&rect=38%2C130%2C5067%2C3099&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/492383/original/file-20221028-67386-5tqk25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=380&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492383/original/file-20221028-67386-5tqk25.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=380&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492383/original/file-20221028-67386-5tqk25.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=380&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492383/original/file-20221028-67386-5tqk25.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=477&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492383/original/file-20221028-67386-5tqk25.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=477&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492383/original/file-20221028-67386-5tqk25.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=477&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Biomimetic mesh surfaces, which mimic penguin feathers with a woven stainless steel textile, showed about 95 per cent decreased ice adhesion strength compared to polished smooth monolithic stainless steel surfaces.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/miriagrunick/32072866901/in/album-72157678813166476/">(MiriaGrunick/flickr)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>This is in contrast to the majority of water-repellant surfaces that mimic air-trapping as seen in lotus leaves (<a href="https://www.futurity.org/superhydrophobic-materials-nontoxic-1067122-2/">lotus effect</a>), where water penetration often strengthens the adhesion of ice. </p>
<p>Our biomimetic mesh surfaces — which mimicked penguin feathers with a woven stainless steel textile — showed about 95 per cent decreased ice adhesion strength compared to polished smooth monolithic stainless steel.</p>
<p>This extremely good ice-shedding performance can be attributed to the shape of the microstructure pores, the openings of which are smaller than the actual empty space inside the pore. </p>
<p>These pore openings get closed off first by growing ice, which traps still liquid water inside. That enclosed water freezes slowly in comparison to the water on the outside. As it freezes, it can expand by around nine per cent in its confined space, ultimately creating cracks along every single pore of the wire cloth. These cracks help any ice build up to shed off easily.</p>
<h2>A de-icing strategy for the future</h2>
<p>While our study approaches the problem of ice accumulation from a different perspective than all previous studies, it provides potential new de-icing solutions to a problem that affects our lives every winter. </p>
<figure class="align-center ">
<img alt="A house roof riddled with icicles." src="https://images.theconversation.com/files/503368/original/file-20230106-26-zu5v7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503368/original/file-20230106-26-zu5v7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503368/original/file-20230106-26-zu5v7f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503368/original/file-20230106-26-zu5v7f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503368/original/file-20230106-26-zu5v7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503368/original/file-20230106-26-zu5v7f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503368/original/file-20230106-26-zu5v7f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">De-icing techniques that mimic penguin feather structures can be used alongside heating systems to prevent icicle formation on house roofs.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/inthe-arena/11760235066/in/photolist-iVdhay-6YMnK-qq3Qpu-2o4Brnc-2o4Gdte-2mSeiEh-2ky5mLv-2kDBiCL-iNXTze-C8i6v9-SE6LkF-7CmMw4-7E5MUW-k4u8Q8-7Bmgm7-5UzhLv-7BBUTQ-5VMHRR-2n6zDBW-q3Npch-dZ3TRZ-4jB8bN-7G28vA-PJW3rm-2mTN3qz-91bHsY-2o4DMwq-wu3zJW-5Ua9Wj-9BCDgy-2mTN3rG-9BzHoX-9BzFPD-9BzHTz-2isMwqG-7DmT1r-5KDKXm-xkikC-2mTJNGB-2mTLP9L-2i6Hrxy-94tgQg-2cETbBz-2gMo2iK-9a3NfX-RykhLo-7sL4Yq-2itj189-2nk8rZS-25q9Vmf">(Andrew Seaman/flickr)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Clearly, we need more investigations and developments before critical infrastructure such as aircraft or power lines solely rely on passive de-icing solutions like these. </p>
<p>However, we can implement them alongside traditional active heating systems for less-critical applications like street signs in the foreseeable future. This will allow us to investigate the long-term stability of such textured surfaces, their installation and maintenance costs, and whether or not it curbs the energy and chemical requirements of today’s de-icing techniques.</p><img src="https://counter.theconversation.com/content/193433/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Anne-Marie Kietzig receives funding from the Natural Sciences and Engineering Research Council of Canada (NSERC).</span></em></p><p class="fine-print"><em><span>Michael John Wood 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>Nature takes a unique approach to solving its icy surface problems. We found the solution to de-icing challenges in the feathers of adorable wobble-gaited penguins.Anne-Marie Kietzig, Associate Professor, Department of Chemical Engineering, McGill UniversityMichael John Wood, Mitacs Elevate Post-Doctoral Scholar, McGill UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1492252020-11-16T13:21:46Z2020-11-16T13:21:46ZHow do geese know how to fly south for the winter?<figure><img src="https://images.theconversation.com/files/369377/original/file-20201113-13-7fvj1e.jpg?ixlib=rb-1.1.0&rect=1218%2C0%2C3624%2C2488&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Geese fly day or night, depending on when conditions are best.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/migrating-canada-geese-royalty-free-image/108309781">sharply_done/E+ via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>How do geese know how to fly south for the winter? – Oscar V., age 9, Huntington, New York</strong></p>
</blockquote>
<hr>
<p>To be ready to migrate in the fall, geese start preparing in midsummer. Babies born in the spring are mostly grown up by then. Adult geese <a href="https://doi.org/10.2307/1369611">grow a new set of plumage</a> after shedding their old feathers – a <a href="https://doi.org/10.1007/978-1-4613-0425-8_6">process called molting</a>.</p>
<p>They need flight and body feathers to be in good condition for the long flight ahead, and to insulate their bodies from the winter cold. For a few weeks during this process, geese can’t fly at all, and they stay out on the water to avoid predators.</p>
<p>Geese have a clock in their brain that <a href="https://www.americanscientist.org/article/avian-migration-the-ultimate-red-eye-flight">measures how much sunlight there is each day</a>. The days grow shorter during the late summer and early fall, and that’s how geese know it’s time to get ready for the journey south. Families join together in larger flocks. Geese gorge on grains and grasses to fatten up in preparation for their journey.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/369378/original/file-20201113-19-z06ost.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="two geese tails emerge from water as they look for food" src="https://images.theconversation.com/files/369378/original/file-20201113-19-z06ost.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/369378/original/file-20201113-19-z06ost.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=442&fit=crop&dpr=1 600w, https://images.theconversation.com/files/369378/original/file-20201113-19-z06ost.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=442&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/369378/original/file-20201113-19-z06ost.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=442&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/369378/original/file-20201113-19-z06ost.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=555&fit=crop&dpr=1 754w, https://images.theconversation.com/files/369378/original/file-20201113-19-z06ost.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=555&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/369378/original/file-20201113-19-z06ost.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=555&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Geese fattening up by eating some underwater foods.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/two-canada-geese-searching-for-food-royalty-free-image/1282657623">Jennifer Yakey-Ault/iStock via Getty Images</a></span>
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<h2>When it’s time to go</h2>
<p>There are two different types of bird migration. For most bird species that migrate from temperate climates to the tropics in winter, <a href="https://doi.org/10.1016/j.tree.2011.07.009">migration is instinctual</a>. These birds, such as swallows, orioles and warblers, leave their northern breeding place before weather turns harsh and food becomes scarce.</p>
<p>Most migrate at night, individually rather than in flocks, and they know where to go and how to get there without guidance from parents or other birds. They migrate continuously, except for short stopovers to fuel up on insects, fruit, or seeds before continuing on their way. </p>
<p>Canada geese and other migratory geese species are different. They usually remain in their summer range until the weather is cold, water starts to freeze, and food gets hard to come by. <a href="https://doi.org/10.1111/oik.03121">Once conditions become so tough</a> that they can’t find enough to eat, geese migrate.</p>
<p>Maybe you’ve observed flock members signaling they’re ready to go: <a href="https://doi.org/10.2307/4083454">They honk loudly and point their bills toward the sky</a>. Single families of geese, or flocks of several families together, take off and head south. Flocks join with other flocks. Geese fly by day or night, depending on factors like weather conditions or brightness of the moon.</p>
<p><a href="https://www.jstor.org/stable/4161751">Geese navigate based on experience</a>, using landmarks including rivers, coastlines and mountain ranges. They may also use celestial cues such as the sun and stars. Geese have a physical compass in their head that allows them to <a href="https://doi.org/10.1641/B570207">tell north and south by detecting the Earth’s magnetic field</a>.</p>
<p>Young geese learn the migration route and landmarks by following their parents and other experienced geese. People who have raised and socially bonded with geese have even taught the birds new migration routes by leading them in an ultralight aircraft – as in the movie “<a href="https://www.imdb.com/title/tt0116329/">Fly Away Home</a>.”</p>
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<h2>On their way</h2>
<p>Geese are heavy birds, and they fly fast – over 30 miles per hour – using powerful wing beats, rather than gliding like eagles or vultures. All this flapping for a heavy bird <a href="https://doi.org/10.1111/j.0908-8857.2004.03378.x">takes a lot of energy</a>. Geese work very hard during migration flights. To reduce the effort, geese fly at night when the <a href="https://www.jstor.org/stable/4161751">air is calmer, or in the day when there’s a helpful tailwind</a>; they avoid flying into a headwind that would blow them backward.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/369379/original/file-20201113-15-xo4vqf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="geese fly in a V against a clear sky" src="https://images.theconversation.com/files/369379/original/file-20201113-15-xo4vqf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/369379/original/file-20201113-15-xo4vqf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/369379/original/file-20201113-15-xo4vqf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/369379/original/file-20201113-15-xo4vqf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/369379/original/file-20201113-15-xo4vqf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/369379/original/file-20201113-15-xo4vqf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/369379/original/file-20201113-15-xo4vqf.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">The different wing positions of these greylag geese show their flapping motion, with the individual at the tip of the V working the hardest.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/flock-of-greylag-geese-in-the-sky-royalty-free-image/461948687">Anagramm/iStock via Getty Images</a></span>
</figcaption>
</figure>
<p>In addition, they have another energy-saving trick. To reduce drag and to receive a little extra lift, geese fly close behind and about one wing length to the side of the one immediately in front. When all flock members do this, the familiar V shape appears.</p>
<p>This <a href="https://doi.org/10.1016/0022-5193(83)90110-8">form of drafting, also called vortex surfing</a>, saves a lot of energy. Following another bird at the right distance blocks any headwind. The flapping of the bird ahead creates a forward movement of air called a slipstream, which helps pull the trailing bird forward. And little pockets of spinning air, called vortices, produce lift that helps keep a trailing bird aloft. The same physics explains why fighter jets fly in V formation to conserve fuel.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-bkxG28OUZw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video explains some of the physics of how the V formation helps keep geese up in the sky for less energy.</span></figcaption>
</figure>
<p>The bird at the point of the V, in the front of the flock, gets no advantage from drafting. It is working much harder than the others. When it gets too tired, it drops back and another takes the lead. Recently, ornithologists have discovered that when families migrate together as a flock, the <a href="https://doi.org/10.1111/jav.02392">parents take turns at the tip of the V</a>. The younger geese, which are not as strong, line up along the V behind the lead parent.</p>
<p>Most geese that breed in a particular region will migrate along similar routes, <a href="https://www.ducks.org/conservation/waterfowl-research-science/understanding-waterfowl-the-flyways">called flyways</a>. For example, geese that pass by my house in Northern New York follow the Atlantic flyway. They’ll end up on the Atlantic Coast and migrate south following the shoreline.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/369380/original/file-20201113-15-1k8iqp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="three Canada geese fly over sand dunes" src="https://images.theconversation.com/files/369380/original/file-20201113-15-1k8iqp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/369380/original/file-20201113-15-1k8iqp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=414&fit=crop&dpr=1 600w, https://images.theconversation.com/files/369380/original/file-20201113-15-1k8iqp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=414&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/369380/original/file-20201113-15-1k8iqp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=414&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/369380/original/file-20201113-15-1k8iqp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=520&fit=crop&dpr=1 754w, https://images.theconversation.com/files/369380/original/file-20201113-15-1k8iqp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=520&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/369380/original/file-20201113-15-1k8iqp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=520&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many geese head to the coast and then navigate south along the shoreline.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/canada-geese-over-sand-dunes-at-jones-beach-long-royalty-free-image/639801946">Vicki Jauron, Babylon and Beyond Photography/Moment via Getty Images</a></span>
</figcaption>
</figure>
<p>Rather than migrate nonstop to their wintering grounds, many geese travel in stages, pausing at traditional stopover sites to rest and regain lost fat. Geese from the <a href="https://www.allaboutbirds.org/guide/Canada_Goose/lifehistory">most northern populations travel to the farthest south</a>. More southerly breeding populations don’t migrate as far. This is called leapfrog migration, since the northern geese literally fly over the more southern birds. <a href="https://doi.org/10.2307/3676124">Why this happens is a bit of a mystery</a>, but it’s possible the northern breeders continue further south to avoid competing for food with southern geese that have already found good wintering conditions closer to their summer homes.</p>
<p>Because geese learn migratory routes, they can flexibly adjust where <a href="https://doi.org/10.1111/gcb.14061">they go as conditions change</a>. Goose migration stopover sites and wintering grounds have shifted, for example, because of changes in farming practices, availability of lawns and golf courses, and other changes in land use. Migratory geese are now adjusting when and where they migrate <a href="https://doi.org/10.3389/fevo.2019.00502">as a consequence of global climate change</a>. And some groups of Canada geese have decided <a href="https://doi.org/10.1675/063.034.0403">to just stay put and skip the migration altogether</a>.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/149225/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tom Langen does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Geese honk loudly and point their bills toward the sky when they’re ready to start the migration. Here’s how they know it’s time, how they navigate and how they conserve energy on the grueling trip.Tom Langen, Professor of Biology, Clarkson UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1491192020-11-05T12:31:50Z2020-11-05T12:31:50ZThe mystery of feather origins: how fluffy pterosaurs have reignited debate<figure><img src="https://images.theconversation.com/files/367013/original/file-20201102-23-1l4frn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Reconstruction</span> <span class="attribution"><span class="source">Yuan Zhang</span></span></figcaption></figure><p>When fossils of the oldest known bird, <em>Archaeopteryx</em>, were first discovered almost 160 years ago, the find created a puzzle that has troubled palaeontologists ever since. </p>
<p>These fossils were celebrated for their chimera-like combination of supposedly reptilian features (such as a bony tail and jaws with teeth) and those seemingly unique to birds – in particular, feathers. They helped demonstrate that birds actually evolved from dinosaurs. </p>
<p>But they also presented a major evolutionary problem. The prehistoric feathers were indistinguishable from those of birds today. So it wasn’t clear how or when feathers evolved, and in what kinds of ancient beasts.</p>
<p>Spectacular fossil discoveries from China in the mid-1990s upended our notions of feather evolution, as they revealed that feathers are not, in fact, unique to birds, but also occurred in many dinosaurs. Over the past 30 years, further fossil finds have revealed remarkable details of the evolution of feathers and flight.</p>
<p>Today, more recent discoveries of what appear to be feathered fossils of pterosaurs, the flying cousins of dinosaurs, have led to the theory that feathers first evolved even earlier with the ancestors of all these creatures. But not everyone is convinced, and the debate over the origins of feathers continues.</p>
<h2>Feathered dinosaurs</h2>
<p>Dinosaurs had many more types of feathers than we see in birds today. Some dinosaurs had four wings. Some species dispensed with wings altogether and glided using <a href="https://link.springer.com/chapter/10.1007/978-3-030-27223-4_5">large flaps of skin</a>). At least some dinosaurs had <a href="https://www.nature.com/articles/nature08740">colourful feathers</a>, used for <a href="https://science.sciencemag.org/content/327/5971/1369">camouflage and mating displays</a>. </p>
<p>And as feathers evolved, so too did the skin of dinosaurs and birds – even starting to <a href="https://www.nature.com/articles/s41467-018-04443-x">produce dandruff</a>. But still, for many years, feathers were known only from maniraptoran dinosaurs (the group of species which actually includes birds). </p>
<p>There were hints that feather evolution wasn’t that simple. Feather-like structures, also termed “protofeathers”, were reported in <a href="https://www.nature.com/articles/20670">ornithischian dinosaurs</a>. Theoretical models predict that the first feathers would have resembled <a href="https://prumlab.yale.edu/publications/evolutionary-origin-and-diversification-feathers">hair-like filaments</a>. The simple hair-like shape of the fossil filaments, however, led some workers to doubt whether they really were feathers, rather than degraded remains of some other material, such as skin collagen. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/367004/original/file-20201102-19-1uwg2oi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Illustration of a grey two-legged dinosaur with feathers." src="https://images.theconversation.com/files/367004/original/file-20201102-19-1uwg2oi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/367004/original/file-20201102-19-1uwg2oi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/367004/original/file-20201102-19-1uwg2oi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/367004/original/file-20201102-19-1uwg2oi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/367004/original/file-20201102-19-1uwg2oi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/367004/original/file-20201102-19-1uwg2oi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/367004/original/file-20201102-19-1uwg2oi.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"></a>
<figcaption>
<span class="caption"><em>Kulindadromeus</em> was one of the earliest known dinosaurs with feathers.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Kulindadromeus_NT_small.jpg">Nobu Tamura/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In 2014, a Jurassic ornithischian dinosaur from Siberia known as <em>Kulindadromeus</em> <a href="https://science.sciencemag.org/content/345/6195/451">was discovered</a> that had both simple monofilaments and more complex feathers emerging from its skin. This dinosaur confirmed that feathers are not just a feature of maniraptoran dinosaurs, but probably originated before the major dinosaur groups diverged. </p>
<p>Clearly, the ability to grow feathers evolved with dinosaurs, although some dinosaur groups, especially the large sauropsids and the armoured ankylosaurs and stegosaurs, may have later lost this ability. But having skin outgrowths (hair), and later losing them is well known in mammals, including whales and elephants.</p>
<p>The question has become not whether feathers are unique to birds, but whether they are unique even to dinosaurs. Fuzzy hair-like fibres reminiscent of dinosaurian “protofeathers” have been known for some time in pterosaurs. The pterosaur filaments were traditionally termed “pycnofibres” and were considered distinct from feathers in form and evolution. </p>
<p>But in 2018 <a href="https://www.nature.com/articles/s41559-018-0728-7">we discovered</a> simple filaments and, remarkably, three types of branched feathers preserved in pterosaurs from the Yanliao Biota fossil deposits from the mid-Jurassic epoch, located in China. Although the branching structure is not quite the same as in birds today, the feathers are rich in keratin, the protein commonly found in feathers and hair, and contain colour-bearing melanosomes. </p>
<p>This discovery strongly suggests that the fuzzy pycnofibres of other pterosaurs are also primitive feathers. This likely means that the ability to grow feathers evolved once, around 100 million years before <em>Archaeopteryx</em>, and was passed down to various groups of species.</p>
<p>Not surprisingly, this notion of feathery pterosaurs has proven contentious and other researchers <a href="https://www.nature.com/articles/s41559-020-01308-9">have challenged our ideas</a>. The <a href="https://www.nature.com/articles/s41559-020-01309-8">debate focuses</a> on a few key issues, with questions regarding preservation of the feathers front and centre.</p>
<p>Leicester University’s Dave Unwin and Portsmouth University’s Dave Martill argue that the pterosaur structures may be too degraded for us to be certain that they are feathers, and that they could actually be degraded skin fibres. But the characteristics of the feathers aren’t consistent with degradation and unravelling of composite fibres. They are also sinuous and lack the spatial organisation of skin fibres and contain melanosomes, which are not incorporated into skin collagen.</p>
<p>Unwin and Martill also point out that the keratin and other chemical evidence we found could be contamination. But this seems unlikely because it was only found in the feathers and not in the surrounding tissue.</p>
<p>Another issue is that other pterosaur fossils only have simple hair-like filaments and not branched structures. But birds today have many different feather types, so these filaments could be a different or early, simple form of feather – an idea supported by the theoretical models.</p>
<h2>Ongoing debate</h2>
<p>It is always a good idea to question interpretations of new fossils, especially where the evolutionary implications are far-reaching, although we believe the evidence for pterosaur feathers is there in the fossils. Clearly, however, there is more to be done, and we are currently conducting more tests on the fossils in order to better understand the chemical composition and structure of the feathers. </p>
<p>Ultimately, if we are correct, it seems that the first feathers will be found in the ancestors of pterosaurs and dinosaurs in the Early Triassic epoch, roughly 252 million to 247 million years ago. Unfortunately, we don’t have any fossils showing soft tissue preservation from this time period. </p>
<p>But if we’ve learned anything from the fossil record of feathers, it’s to expect that more will be discovered. Over the years we’ve had to repeatedly broaden our search for fossils with feathers, and for what ancient feathers looked like. Who knows what insights future fossils will bring.</p><img src="https://counter.theconversation.com/content/149119/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Maria McNamara is a palaeobiologist at University College Cork. Her current research is funded by the European Research Council and Science Foundation Ireland. </span></em></p><p class="fine-print"><em><span>Zixiao Yang is a PhD student in palaeontology at Nanjing University. His current research is funded by the China Scholarship Council.</span></em></p>Did feathers evolve in the common ancestor of pterosaurs and dinosaurs? Not everyone is convincedMaria McNamara, Senior Lecturer in Geology, University College CorkZixiao Yang, PhD Candidate in Palaeontology, Nanjing UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1353782020-04-03T18:01:11Z2020-04-03T18:01:11ZBlue dye from red beets – chemists devise a new pigment option<figure><img src="https://images.theconversation.com/files/324753/original/file-20200401-23143-1032w4i.jpg?ixlib=rb-1.1.0&rect=233%2C170%2C1715%2C1386&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Through the wonders of chemistry, molecules can be rearranged to completely transform color.</span> <span class="attribution"><span class="source">Erick Leite Bastos</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>What’s your favorite color? If you answered blue, you’re in good company. <a href="https://today.yougov.com/topics/lifestyle/articles-reports/2015/05/12/why-blue-worlds-favorite-color">Blue outranks all other color preferences</a> worldwide by a large margin.</p>
<p>No matter how much people enjoy looking at it, blue is a difficult color to harness from nature. As a chemist who <a href="https://www.bastoslab.com/">studies the modification of natural products</a> to solve technological problems, I realized there was a need for a safe, nontoxic, cost-effective blue dye. So my Ph.D. student, Barbara Freitas-Dörr, and I devised a <a href="https://advances.sciencemag.org/content/6/14/eaaz0421">method to convert the pigments of red beets into a blue compound</a> that can be used in a wide range of applications. We call it BeetBlue.</p>
<h2>Natural sources of blue</h2>
<p>Blue is strongly associated with nature, largely because it is reflected in the sky and on bodies of water. But compared to other colors, blue pigments are not commonly found in living organisms.</p>
<p>The feathers of many birds are blue, not because they produce a pigment, but because the microscopic structure of their <a href="https://en.wikipedia.org/wiki/Structural_coloration">feathers is able to filter light</a>. This physical phenomenon is very interesting but difficult to adopt for common applications.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.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"></a>
<figcaption>
<span class="caption">The <em>Lactarius indigo</em> mushroom is one of Mother Nature’s rare examples of blue.</span>
<span class="attribution"><a class="source" href="https://de.wikipedia.org/wiki/Datei:2013-08-06_Lactarius_indigo_(Schwein.)_Fr_359786.jpg">Alan Rockerfeller/Mushroom Observer</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Plants seldom produce blue hues. When they do, their pigments rarely remain stable after extraction. The same is true for blue mushrooms like the indigo milky cap and other species that develop a blue stain when disturbed. </p>
<h2>Turning red into blue</h2>
<p>You might wonder how something red can be turned into something blue. One approach is to change the way its molecules absorb and reflect light.</p>
<p>The white light coming from your lamp contains a rainbow of colors, even though you cannot see them – without the use of a prism, that is. The surface of your red chair looks red because, at the molecular level, it is absorbing all the colors except red, which is reflected and eventually reaches your eyes.</p>
<p>The color of your chair would change from red to blue if you modified the molecular structure of its dye, making it reflect blue light instead of red. The secret is in the number of carbon atoms in the dye and how they are connected to each other. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=148&fit=crop&dpr=1 600w, https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=148&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=148&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=185&fit=crop&dpr=1 754w, https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=185&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=185&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">By changing the structure of molecular compounds, you can alter color.</span>
<span class="attribution"><span class="source">Erick Leite Bastos</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Beets produce chemical compounds called betalains, which are natural pigments and antioxidants. The chemical structure of betalains can be modified to produce almost any hue. We realized that if we increased the number of alternating single-double bonds in betalain molecules, we could change their color from orange or magenta to blue.</p>
<p>Making blue dye with adequate intensity and light-fastness is difficult because it must absorb yellow and orange light efficiently. Solving this problem required lots of molecular tweaking.</p>
<p>My lab has been working with betalains for over 10 years to understand their function in nature and their unique chemical features, so it took only one experiment to produce BeetBlue. (It took more than two years to optimize the process, though.) </p>
<p>We broke apart the betalain molecules using alkaline water with a pH of 11. Then we mixed the resulting compound, called betalamic acid, with a commercial chemical compound called 2,4-dimethylpyrrole in an open vessel at room temperature. BeetBlue is formed almost instantly. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/FUS95BYqJ24?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">BeetBlue is created in a beaker at room temperature.</span></figcaption>
</figure>
<p>Because we changed the characteristic carbon-nitrogen chemical bond of betalains into a carbon-carbon bond, BeetBlue is a new class of pseudo-natural dyes we call quasibetalains.</p>
<h2>Color your life blue</h2>
<p>The chemical synthesis of BeetBlue is fast and very simple. In fact, it is so simple that anyone can do it if all the chemicals are available.</p>
<p>BeetBlue dissolves easily in water and other solvents, maintains its color in acidic and neutral solutions, and may provide an alternative to expensive blue colorants that often <a href="https://en.wikipedia.org/wiki/List_of_inorganic_pigments#Blue_pigments">contain toxic metals</a>, which limit the scope of their applications. </p>
<p>Live zebrafish embryos as well as cultured human cells were not affected by BeetBlue. Although more experiments are necessary to make sure it is safe for human consumption, maybe you can dye your hair, customize your clothes or color your food in the future using a dye made from beets.</p>
<p>This work shows the importance of basic science for the development of technological applications. We did not patent BeetBlue. We want people to use it freely and understand, by interacting with nature in a different and sustainable way, the future can be bright. </p>
<p>[<em>Insight, in your inbox each day.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=insight">You can get it with The Conversation’s email newsletter</a>.]</p><img src="https://counter.theconversation.com/content/135378/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Erick Leite Bastos receives funding from the São Paulo Research Foundation (FAPESP), the Brazilian National Council for Scientific and Technological Development (CNPq), and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).</span></em></p>A simple chemical reaction turns the red pigment of beets into a new, nontoxic blue dye.Erick Leite Bastos, Associate Professor of Chemistry, Universidade de São Paulo (USP)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1039052018-09-30T20:04:20Z2018-09-30T20:04:20ZI’ve Always Wondered: why did mammals go the fur route, rather than developing feathers?<figure><img src="https://images.theconversation.com/files/237994/original/file-20180926-149979-1izpfs0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Birds and mammals use feathers and fur for staying warm and dry – but for other purposes too. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/closeup-eclectus-parrot-bassett-hound-puppy-1423051?src=7zA95dP7nX_BDircZRTnRQ-1-9">from www.shutterstock.com </a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/ive-always-wondered-43449">I’ve Always Wondered</a>, a series where readers send in questions they’d like an expert to answer. Send your question to alwayswondered@theconversation.edu.au</em></p>
<hr>
<p><strong>Assuming feathers are superior to fur in terms of water protection and insulation, I’ve always wondered: why did mammals go the fur route, rather than developing feathers? – Shane, Perth</strong> </p>
<p>One of the main characteristics that distinguish mammals from birds, and other animals, is that mammals have hair or fur, and birds have feathers. </p>
<p>Mammals evolved from the <a href="https://cosmosmagazine.com/palaeontology/before-the-dinosaurs">synapsids</a> (such as the finback, <em>Dimetrodon</em>) between 320 and 315 million years ago, while birds evolved from <a href="https://blogs.scientificamerican.com/tetrapod-zoology/50-million-years-of-incredible-shrinking-theropod-dinosaurs/">theropod dinosaurs</a> (like <em>T.rex</em>) around 150 million years ago. So hair and feathers evolved separately from different groups of animals. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-many-dinosaurs-in-total-lived-on-earth-during-all-periods-100460">Curious Kids: How many dinosaurs in total lived on Earth during all periods?</a>
</strong>
</em>
</p>
<hr>
<p>While each group of animals requires varying degrees of insulation and waterproofing, the different animals also use hair and feathers for additional purposes – like sensing their environment, and courting displays. Together, all these roles affect an animal’s chances of survival and finding a mate to successfully reproduce with. </p>
<p>Both fur and feathers are part of the <a href="https://biologydictionary.net/integumentary-system/">integumentary system</a>, associated with the external covering of the body.</p>
<h2>Hair for heat control</h2>
<p>Often, we associate hair or fur with insulation. Sheep hair, called wool, is well recognised for its capacity to insulate, and humans have built whole industries based on its properties. </p>
<p>Of course, the number, type and colour of hair differs among mammalian species, and these characteristics are based on the specific mammal’s needs. </p>
<p>Hairs are always associated with sebaceous glands (that produce sebum, a water repellent-like substance) and sensory receptors. </p>
<p>The naked mole-rat (<em>Heterocephalus glaber</em>), a blind subterranean mammal, has some scattered hairs (despite its name) – it uses these to navigate through associated <a href="https://oercommons.s3.amazonaws.com/media/thumbnails/22/00/220044edf76ab7d8cd0050a942a0a313.jpg">sensory receptors</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/237995/original/file-20180926-149979-2gv1qw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/237995/original/file-20180926-149979-2gv1qw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/237995/original/file-20180926-149979-2gv1qw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/237995/original/file-20180926-149979-2gv1qw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/237995/original/file-20180926-149979-2gv1qw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/237995/original/file-20180926-149979-2gv1qw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/237995/original/file-20180926-149979-2gv1qw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Despite its name, hairs on the naked mole rat provide sensory information to help it navigate underground.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/naked-mole-rat-heterocephalus-glaber-tube-92428237?src=aq57HaKwL4klZY8kSFBXiA-1-12">from www.shutterstock.com</a></span>
</figcaption>
</figure>
<p>Elephants also appear essentially hairless; however, they are covered in hair of varying lengths and densities. Like their ancestors the mammoths, modern day elephants have a large volume-to-surface-area ratio. So rather than an insulator, modern-day elephant hair enables heat loss and aids cooling.</p>
<p>Individual hair strands are different colours. The outer portion of the hair strands are responsible for the general appearance of the animal, and hence, its overall colouration. The inner portion of the hair strand is responsible for insulation.</p>
<p>Hair or coat colour affects the ability of hair to reflect solar radiation and insulate. Dark hair absorbs more radiant heat than lighter hair. For example, in the arid zones of outback Australia, the darker euro (also referred to as the common wallaroo, <em>Macropus robustus</em>) avoids heat behaviourally by moving <a href="https://www.sciencedirect.com/science/article/pii/0010406X70909540?via%3Dihub">out of the sun</a>. The lighter-coloured red kangaroo (<em>Macropus rufus</em>) spends more time in open areas. </p>
<p>So hair colour is important for species who use basking in the sun to warm themselves and conserve energy.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/237997/original/file-20180926-149985-4aw7mv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/237997/original/file-20180926-149985-4aw7mv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/237997/original/file-20180926-149985-4aw7mv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/237997/original/file-20180926-149985-4aw7mv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/237997/original/file-20180926-149985-4aw7mv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/237997/original/file-20180926-149985-4aw7mv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/237997/original/file-20180926-149985-4aw7mv.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">Just catching some rays – because I can.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/red-kangaroo-macropus-rufus-wildlife-animal-507249961?src=vy_C0VeWMwISF9COx2erjQ-1-1">from www.shutterstock.com</a></span>
</figcaption>
</figure>
<h2>Hair for defence</h2>
<p>Zebras (<em>Equis</em> species) have black and white striped fur to reduce insect attack and confuse biting flies. Scientists have found all white or all dark coloured horse species and related species are <a href="https://www.youtube.com/watch?time_continue=5&v=cgyDrHEDc7Q">more readily bitten by flies than striped zebras</a>. </p>
<p>Hair can also play a role in defence for species such as porcupines, echidnas and hedgehogs. Porcupines have modified hairs called quills, while echidnas and hedgehogs have hollow spines, both covered in a thick layer of keratin. The animals also have bristles, underfur, and/or hair among their quills or spines, and on their bellies. </p>
<p>Hedgehogs roll into a tight ball and expose their spiny backs towards predators. Smilarly, echidnas can curl into a ball or will bury themselves and leave their spiny backs exposed as protection from predators.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/238000/original/file-20180926-149961-1ewhilx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/238000/original/file-20180926-149961-1ewhilx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/238000/original/file-20180926-149961-1ewhilx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/238000/original/file-20180926-149961-1ewhilx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/238000/original/file-20180926-149961-1ewhilx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/238000/original/file-20180926-149961-1ewhilx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/238000/original/file-20180926-149961-1ewhilx.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">Echidna quills are actually modified hairs.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/148286771@N02/33128078282/in/photolist-Stq4vu-dZVPsC-6NxszS-7kgVJ5-69Zuu7-7dyYV8-7kd2tv-7dyZ1T-28qfcoV-5gEo5j-79vZCM-U3QLXW-7kgVUh-27g1m71-hfHQJV-8cJApA-LgdTjc-SsE6cf-7omQSi-isZ9MD-8zE2a6-on5H6t-hfJpGj-8zHaYo-ApYG5J-rpCgHA-KeHD6U-c33czu-am8rwR-q1U5rL-c32QNs-hfJgZo-meysSR-g8JUb1-9aFnnz-c32Xkh-hfJyof-29xQC73-6zU7qo-c33hsj-c32Rsy-8vSPPV-e6ofEw-c335B9-8vX6mJ-AaFCM3-69MsCR-c32Z9Q-5BNEUc-rBXrVo">148286771@N02/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<h2>Types of feathers</h2>
<p>So, what about feathers? Just like mammals have sensory receptors associated with hairs, birds have sensory receptors associated with feathers. These enable birds to sense objects such as biting flies and other parasites. </p>
<p>There are two main types of feathers: vaned feathers and down feathers. </p>
<p>Vaned feathers have a rachis or shaft, with barbs branching off, and smaller barbules branching off the barbs. Down feathers lack barbles, and are fluffy in appearance. </p>
<p>Down feathers are responsible for insulation, and are the feathers we use in our doonas, whilst vaned feathers aid flight.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/238002/original/file-20180926-149964-ty8d0j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/238002/original/file-20180926-149964-ty8d0j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=515&fit=crop&dpr=1 600w, https://images.theconversation.com/files/238002/original/file-20180926-149964-ty8d0j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=515&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/238002/original/file-20180926-149964-ty8d0j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=515&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/238002/original/file-20180926-149964-ty8d0j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=647&fit=crop&dpr=1 754w, https://images.theconversation.com/files/238002/original/file-20180926-149964-ty8d0j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=647&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/238002/original/file-20180926-149964-ty8d0j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=647&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Different types of feathers suit different purposes – flight, warmth and mating displays.
1 - contour/flight feather, 2 - steering feather (tail feather), 3 - covering feather, 4 - piliform feather, 5 - bump feather, 6 - down feather.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Types_of_feathers.jpg">Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>In some birds, the barbles on vaned feathers produce a powder that aids waterproofing. </p>
<p>Birds also have a <a href="https://www.penguinscience.com/education/src/ap_7.jpg">uropygial gland</a> located towards the base of their tail. It provides wax-like substances to aid feather preening and maintenance, and likely provides an additional water proofing as well.</p>
<p>There is one further type of feather, that is very specialised: the piloplume. These feathers are used by males to display to females and attract a mate. Generally speaking, this is why male birds are often more colourful than female birds. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/238003/original/file-20180926-149967-yztvnq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/238003/original/file-20180926-149967-yztvnq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/238003/original/file-20180926-149967-yztvnq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/238003/original/file-20180926-149967-yztvnq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/238003/original/file-20180926-149967-yztvnq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/238003/original/file-20180926-149967-yztvnq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/238003/original/file-20180926-149967-yztvnq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">These tail feathers have the sole function of looking good.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Peacock_Wooing_Peahen.jpg">Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Mammals use different methods to display to females and to attract mates. Deer display strength and agility to females through antlers, whales use song, while other mammals, such as cats, use scent.</p>
<p>Finding a mate is of course essential to produce the next generation. And feathers and fur play key roles in making sure that happens. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/YTR21os8gTA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">New Guinea’s spectacular birds of paradise.</span></figcaption>
</figure><img src="https://counter.theconversation.com/content/103905/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hayley J Stannard received funding from an Australian Research Council Linkage Grant (2015-2018). </span></em></p><p class="fine-print"><em><span>Julie Old 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>Finding a mate is of course essential to produce the next generation. And feathers and fur play key roles in making sure that happens.Julie Old, Associate Professor, Biology, Zoology, Animal Science, Western Sydney UniversityHayley Stannard, Lecturer, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/896892018-01-09T16:01:26Z2018-01-09T16:01:26ZSuper-black feathers can absorb virtually every photon of light that hits them<figure><img src="https://images.theconversation.com/files/201228/original/file-20180108-142334-1h044en.jpg?ixlib=rb-1.1.0&rect=0%2C54%2C925%2C708&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Super-black feathers on these guys are like looking into a dark cave.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/sdnatasha/4514108926">Natasha Baucas</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>What do birds and aerospace engineers have in common? Both have invented incredibly dark, “super-black” surfaces that absorb almost every last bit of light that strikes them. </p>
<p>Of course scientists worked intentionally to devise these materials. It’s evolution that brought this amazing trait about in birds. My co-lead author <a href="http://vertebrates.si.edu/birds/birds_staff_pages/TeresaFeo_staffpage.html">Teresa Feo</a>, our colleagues <a href="http://www.graphics.cornell.edu/%7Etodd/pcg/Home.html">Todd A. Harvey</a> and <a href="https://prumlab.yale.edu/">Rick Prum</a> and I <a href="http://nature.com/articles/doi:10.1038/s41467-017-02088-w">investigated the super-black feathers</a> in some of the most outlandish animals on earth: <a href="http://www.birdsofparadiseproject.org/">the Birds of Paradise</a>.</p>
<p>These are resplendent birds native to Papua New Guinea and surrounding areas. Males are brilliantly colored, with complicated mating dances. Females, who are drab and brown in comparison, carefully inspect the ornaments and dances of males before choosing their mate.</p>
<p>We wanted to know more about these birds’ super-black plumage and how it works. What mechanism do these feathers employ to be so effective at absorbing light?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/201237/original/file-20180108-83581-d443ug.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/201237/original/file-20180108-83581-d443ug.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/201237/original/file-20180108-83581-d443ug.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/201237/original/file-20180108-83581-d443ug.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/201237/original/file-20180108-83581-d443ug.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/201237/original/file-20180108-83581-d443ug.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/201237/original/file-20180108-83581-d443ug.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/201237/original/file-20180108-83581-d443ug.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">A male Superb Bird of Paradise displays his super-black and brilliant blue plumage to an onlooking female.</span>
<span class="attribution"><span class="source">Ed Scholes</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Fanciest feathers, under the microscope</h2>
<p>The Birds of Paradise have evolved many remarkable traits, but none are more mysterious than the males’ velvety black plumage.</p>
<p>This black is so dark that your eyes cannot focus on its surface; it looks like a cave, or a fuzzy black hole in space. Using optical measurements, we found that these feather patches <a href="http://nature.com/articles/doi:10.1038/s41467-017-02088-w">absorb up to 99.95 percent of directly incident light</a>. That’s comparable to human-made very black materials such as solar panels, the lining of space telescopes, and even the “blackest black” material: <a href="http://www.cnn.com/2017/11/15/world/vantablack-blackest-black-material/index.html">Vantablack</a>, which absorbs 99.96 percent of light.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/201235/original/file-20180108-83567-ish8tm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/201235/original/file-20180108-83567-ish8tm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/201235/original/file-20180108-83567-ish8tm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=298&fit=crop&dpr=1 600w, https://images.theconversation.com/files/201235/original/file-20180108-83567-ish8tm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=298&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/201235/original/file-20180108-83567-ish8tm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=298&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/201235/original/file-20180108-83567-ish8tm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=374&fit=crop&dpr=1 754w, https://images.theconversation.com/files/201235/original/file-20180108-83567-ish8tm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=374&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/201235/original/file-20180108-83567-ish8tm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=374&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">On the left, a normal black feather from a Lesser Melampitta. On the right, a super-black feather from the Paradise Riflebird.</span>
<span class="attribution"><span class="source">Dakota McCoy</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Normal feathers are flat, and look like fractals; when you zoom in using a microscope, each branch of the feather looks like a tiny, flat feather. Under a powerful scanning electron microscope, we were surprised to see that the super-black feathers look like miniature coral reefs, bottle brushes or trees with tightly packed leaves.</p>
<p>These tiny, specially shaped bits stick up to form a jagged, complex surface; together they act as microscopic light traps. When light rays strike these surface microstructures, they repeatedly scatter around the shapes and are absorbed, rather than being reflected back to an observer. It’s an iterative process: Each time a scattering event occurs, a portion of the light is absorbed until it’s almost completely absorbed.</p>
<p>Human-made super-black materials such as “<a href="https://www.pv-tech.org/guest-blog/black-silicon-theres-more-than-meets-the-eye">black silicon</a>” also rely on what materials scientists call structural absorption. Like the super-black feathers, their microscopic “<a href="https://doi.org/10.1063/1.4719108">light traps</a>” are due to a rough surface that scatters light repeatedly, but the actual surface shapes they use are different. Rather than the feathers’ bottle brush shapes, human engineers designed regularly spaced microscopic cones and pits. With almost no exposed flat surface, these structurally black materials are the opposite of a mirror.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/201236/original/file-20180108-83556-1i5x62g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/201236/original/file-20180108-83556-1i5x62g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/201236/original/file-20180108-83556-1i5x62g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=301&fit=crop&dpr=1 600w, https://images.theconversation.com/files/201236/original/file-20180108-83556-1i5x62g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=301&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/201236/original/file-20180108-83556-1i5x62g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=301&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/201236/original/file-20180108-83556-1i5x62g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=378&fit=crop&dpr=1 754w, https://images.theconversation.com/files/201236/original/file-20180108-83556-1i5x62g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=378&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/201236/original/file-20180108-83556-1i5x62g.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">Due to its unusual microstructure, the feather from the Paradise Riflebird (on the right) still appears super-black when coated with gold, as compared to a regular black feather (on the left).</span>
<span class="attribution"><span class="source">Dakota McCoy</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The Birds of Paradise’s super-black feathers are so good at absorbing light that even when we coated them in gold, a shiny metal, they still looked black. That’s because it’s not the inside of the feather making the color via pigment or ordered nanostructures; instead, just as with human-made <a href="https://doi.org/10.1039/C4EE01152J">black silicon</a>, the super black comes from the physical surface structure. Evolution and human ingenuity arrived at the same solution.</p>
<h2>Advantages of super-black feathers</h2>
<p>But why do these birds have such incredibly dark black patches? What selective advantage caused this trait to evolve? It’s tempting to think that super black somehow helps with camouflage, to keep predators away. In fact, some <a href="https://doi.org/10.1038/srep01846">snakes have super-black scales</a> that mimic shadows between leaves, helping them blend into the forest floor. The snake example illustrates evolution by natural selection – “survival of the fittest.”</p>
<p>But other factors can also influence evolution’s course, including random chance or sexual selection. As my colleague Rick Prum points out in his new book “<a href="https://www.penguinrandomhouse.com/books/224257/the-evolution-of-beauty-by-richard-o-prum/9780385537216/">The Evolution of Beauty: How Darwin’s Forgotten Theory of Mate Choice Shapes the Animal World – and Us</a>,” mate choice is a powerful force driving evolution. In Birds of Paradise, super-black feathers help male birds look more beautiful to a female’s eye.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/UYbn9R11Rrs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A Superb Bird of Paradise displays his best plumage to potential mate.</span></figcaption>
</figure>
<p>To understand how, it helps to look at Bird of Paradise mating dances. Males vigorously display their super-black patches to females, making sure that females can’t get a view from the side. This is because these feathers are highly directional, and they look darkest from straight ahead. </p>
<p>And super-black patches always sit around or next to brilliant color patches. A super-black, anti-reflective frame makes nearby colors appear brighter, almost glow. In other words, super black is an <a href="https://en.wikipedia.org/wiki/Checker_shadow_illusion">evolved optical illusion</a> that relies on the way animal eyes and brains adjust our perceptions based on ambient light.</p>
<p>In the high-stakes game of choosing a mate, a single feather that isn’t quite blue enough <a href="https://www.penguinrandomhouse.com/books/224257/the-evolution-of-beauty-by-richard-o-prum/9780385537216/">could be enough to turn off</a> a female Bird of Paradise. Clearly, female Birds of Paradise prefer males with super-black plumage. As females <a href="https://doi.org/10.1111/evo.13196">pick the most impressive males to mate with</a>, those dazzling feather genes are passed on to future generations while the genes of less splendid males, overlooked by females, are not. Sexual selection drove evolution toward super-black plumage.</p>
<p>Evolution is not an orderly, coherent process; evolutionary arms races can produce great innovation. Perhaps these super-black feathers with their unique microscopic structure could eventually inspire better solar panels, or new textiles; super-black butterfly wings <a href="https://link.springer.com/article/10.1186/s11671-015-1052-7">already have</a>. Evolution has had millions of years to tinker; we still have much to learn from its solutions.</p><img src="https://counter.theconversation.com/content/89689/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>This research was
funded by the W. R. Coe Fund of Yale University, by a Sigma XI student research
fellowship to D.E.M., and by a Mind, Brain, and Behavior Graduate Student Award
to D.E.M. D.E.M. was supported by the Department of Defense (DoD) through the
National Defense Science and Engineering Graduate Fellowship (NDSEG)
Program. Tomography data collections at the Advanced Photon Source beamline 2-
BM, Argonne National Laboratory were supported by the U.S. Department of
Energy Office of Science (Proposal ID 41887). T.J.F. was supported by a NSF
Postdoctoral Fellowship in Biology (#1523857). Richard Pfisterer of Photon
Engineering graciously licensed FRED to T.A.H. for this research. This work was
performed in part at the Harvard University Center for Nanoscale Systems (CNS), a
member of the National Nanotechnology Coordinated Infrastructure Network
(NNCI), which is supported by the National Science Foundation under NSF ECCS
award no. 1541959.</span></em></p>Male Birds of Paradise have patches of super-black plumage that absorb 99.95 percent of light. New research identified their feathers’ microscopic structures that make them look so very dark.Dakota McCoy, PhD Student in Organismic and Evolutionary Biology, Harvard UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/870852017-11-09T19:19:40Z2017-11-09T19:19:40ZThose noisy crested pigeons use their unique feathers to sound an alarm<figure><img src="https://images.theconversation.com/files/193690/original/file-20171108-6733-aiwxzv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Crested pigeon in flight with the primary feathers spread and the narrow eighth primary is visible.</span> <span class="attribution"><span class="source">Geoffrey Dabb</span>, <span class="license">Author provided</span></span></figcaption></figure><p><a href="http://birdlife.org.au/bird-profile/Crested-Pigeon">Crested pigeons</a> are a common sight in many Australian backyards, and are noted for the rapid trilling sound they make when they take flight.</p>
<p>In our research, <a href="http://www.cell.com/current-biology/fulltext/S0960-9822(17)31268-X">published today in Current Biology</a>, we show that these sounds are produced by feathers in the wings that have evolved to communicate about danger.</p>
<p><audio preload="metadata" controls="controls" data-duration="2" data-image="" data-title="Recording of a pigeon fleeing from a predator" data-size="37297" data-source="Trevor Murray" data-source-url="" data-license="Author provided" data-license-url="">
<source src="https://cdn.theconversation.com/audio/966/recording-of-a-pigeon-fleeing-from-a-replica-predator-credit-trevor-murray.mp3" type="audio/mpeg">
</audio>
<div class="audio-player-caption">
Recording of a pigeon fleeing from a predator.
<span class="attribution"><span class="source">Trevor Murray</span>, <span class="license">Author provided</span><span class="download"><span>36.4 KB</span> <a target="_blank" href="https://cdn.theconversation.com/audio/966/recording-of-a-pigeon-fleeing-from-a-replica-predator-credit-trevor-murray.mp3">(download)</a></span></span>
</div></p>
<p>These sounds were <a href="http://www.abc.net.au/science/articles/2009/09/02/2674184.htm">long suspected of being produced by the wings</a>, so we used high-speed video and acoustic recording to investigate this. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/citizen-scientists-count-nearly-2-million-birds-and-reveal-a-possible-kookaburra-decline-86469">Citizen scientists count nearly 2 million birds and reveal a possible kookaburra decline</a>
</strong>
</em>
</p>
<hr>
<p>The key finding is that a pair of unusual primary flight feathers, half the width of the others, produce a high-pitched sound as the wing pushes down through the air. This sound is a critical part of the alarm signal that warns the flock. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/193871/original/file-20171109-14209-1qp0qxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/193871/original/file-20171109-14209-1qp0qxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/193871/original/file-20171109-14209-1qp0qxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=444&fit=crop&dpr=1 600w, https://images.theconversation.com/files/193871/original/file-20171109-14209-1qp0qxk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=444&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/193871/original/file-20171109-14209-1qp0qxk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=444&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/193871/original/file-20171109-14209-1qp0qxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=558&fit=crop&dpr=1 754w, https://images.theconversation.com/files/193871/original/file-20171109-14209-1qp0qxk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=558&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/193871/original/file-20171109-14209-1qp0qxk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=558&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 wing of a crested pigeon showing the thinner 8th primary feather.</span>
<span class="attribution"><a class="source" href="https://figshare.com/articles/Feather_Measurements_and_photographs/5418562">Trevor Murray, Robert Magrath and Jochen Zeil</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>No other related pigeon species has these unusually narrow wing feathers. The narrowness of these feathers, known as the the 8th primary feathers, suggests that they have evolved to produce this high-pitched sound.</p>
<h2>Feathers to the test</h2>
<p>We discovered that the 8th primary feathers produce the high-pitched sound, by trimming pairs of feathers and recording the sounds of pigeons fleeing. But we were also interested in how trimming the 8th primary feathers would affect the response of other crested pigeons that heard these modified fleeing sounds.</p>
<p>We developed a speaker set up that let us broadcast the recorded fleeing sounds of birds from the side of a vehicle. We would then drive next to pigeons foraging in parks and on nature strips around Canberra, and broadcast one of the recordings at random. </p>
<p><audio preload="metadata" controls="controls" data-duration="3" data-image="" data-title="Recording of a pigeon released after capture with both 8th primaries removed" data-size="63110" data-source="Trevor Murray" data-source-url="" data-license="Author provided" data-license-url="">
<source src="https://cdn.theconversation.com/audio/967/recording-of-a-pigeon-released-after-capture-with-both-8th-primaries-removed-credit-trevor-murray.mp3" type="audio/mpeg">
</audio>
<div class="audio-player-caption">
Recording of a pigeon released after capture with both 8th primaries removed.
<span class="attribution"><span class="source">Trevor Murray</span>, <span class="license">Author provided</span><span class="download"><span>61.6 KB</span> <a target="_blank" href="https://cdn.theconversation.com/audio/967/recording-of-a-pigeon-released-after-capture-with-both-8th-primaries-removed-credit-trevor-murray.mp3">(download)</a></span></span>
</div></p>
<p>When we played recordings of crested pigeons with both the 8th primary feathers removed, the birds looked up, but almost never flew off.</p>
<p>Our suspicions were correct - this unusual pair of 8th primary feathers and their high-pitched sound were necessary for warning other pigeons to flee. </p>
<p>So what about the neighbouring 9th primary feathers? We discovered that these produce a low-pitched sound during take-off.</p>
<p><audio preload="metadata" controls="controls" data-duration="3" data-image="" data-title="Recording of a pigeon released after capture with both 9th primaries removed" data-size="53497" data-source="Trevor Murray" data-source-url="" data-license="Author provided" data-license-url="">
<source src="https://cdn.theconversation.com/audio/968/recording-of-a-pigeon-released-after-capture-with-both-9th-primaries-removed-credit-trevor-murray.mp3" type="audio/mpeg">
</audio>
<div class="audio-player-caption">
Recording of a pigeon released after capture with both 9th primaries removed.
<span class="attribution"><span class="source">Trevor Murray</span>, <span class="license">Author provided</span><span class="download"><span>52.2 KB</span> <a target="_blank" href="https://cdn.theconversation.com/audio/968/recording-of-a-pigeon-released-after-capture-with-both-9th-primaries-removed-credit-trevor-murray.mp3">(download)</a></span></span>
</div></p>
<p>When we played recordings of crested pigeons with both the 9th primary feathers removed, the birds flew off just as often as if they’d heard an alarm. These feathers were not necessary for warning flock mates.</p>
<h2>All in a flap</h2>
<p>Signals evolve when the creature producing the signal and the one responding to it both benefit. </p>
<p>Crested pigeons that see predators can benefit by inciting the rest of the flock to flee with them, much like redshanks and Belding’s ground squirrels, whose coordinated fleeing confuses predators. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/193691/original/file-20171108-6733-mwpur7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/193691/original/file-20171108-6733-mwpur7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/193691/original/file-20171108-6733-mwpur7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=331&fit=crop&dpr=1 600w, https://images.theconversation.com/files/193691/original/file-20171108-6733-mwpur7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=331&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/193691/original/file-20171108-6733-mwpur7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=331&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/193691/original/file-20171108-6733-mwpur7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=416&fit=crop&dpr=1 754w, https://images.theconversation.com/files/193691/original/file-20171108-6733-mwpur7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=416&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/193691/original/file-20171108-6733-mwpur7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=416&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 pair of crested pigeons on the ground.</span>
<span class="attribution"><span class="source">Geoffrey Dabb</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The benefit from communication to every individual could explain why the 8th primary is so unique - it has evolved to exaggerate the sounds of fleeing to trigger a coordinated response.</p>
<p>While these pigeons always produce some sound when they take off, the sounds produced when fleeing danger are distinct. They are louder and have a higher tempo.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/igk1TvsZyMs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A crested pigeon takes flight in slow motion.</span></figcaption>
</figure>
<p>Footage from high-speed video cameras showed that fleeing pigeons flap faster when trying to escape a threat. Flapping faster speeds up their escape and it also increases the tempo of the sound, thus transforming the take-off sound into an alarm. </p>
<p>While these differences in the sound can be quite subtle to the human ear, crested pigeons are able to respond to them in about a third of a second. (Can you tell the difference between these two sounds?)</p>
<p><audio preload="metadata" controls="controls" data-duration="2" data-image="" data-title="Recording of a pigeon take-off normally from a feeder" data-size="33435" data-source="Trevor Murray" data-source-url="" data-license="Author provided" data-license-url="">
<source src="https://cdn.theconversation.com/audio/970/recording-of-a-pigeon-take-off-normally-from-a-feeder-credit-trevor-murray.mp3" type="audio/mpeg">
</audio>
<div class="audio-player-caption">
Recording of a pigeon take-off normally from a feeder.
<span class="attribution"><span class="source">Trevor Murray</span>, <span class="license">Author provided</span><span class="download"><span>32.7 KB</span> <a target="_blank" href="https://cdn.theconversation.com/audio/970/recording-of-a-pigeon-take-off-normally-from-a-feeder-credit-trevor-murray.mp3">(download)</a></span></span>
</div></p>
<p><audio preload="metadata" controls="controls" data-duration="2" data-image="" data-title="Recording of a pigeon fleeing from a predator" data-size="37297" data-source="Trevor Murray" data-source-url="" data-license="Author provided" data-license-url="">
<source src="https://cdn.theconversation.com/audio/966/recording-of-a-pigeon-fleeing-from-a-replica-predator-credit-trevor-murray.mp3" type="audio/mpeg">
</audio>
<div class="audio-player-caption">
Recording of a pigeon fleeing from a predator.
<span class="attribution"><span class="source">Trevor Murray</span>, <span class="license">Author provided</span><span class="download"><span>36.4 KB</span> <a target="_blank" href="https://cdn.theconversation.com/audio/966/recording-of-a-pigeon-fleeing-from-a-replica-predator-credit-trevor-murray.mp3">(download)</a></span></span>
</div></p>
<p>All animals produce some sound as they move, and these sounds are intrinsically informative. They tell the listener where the individual is and how it is moving. This is in stark contrast to the sounds produced by our voices, which are not the result of specific actions.</p>
<p>The same is true for animals: vocal calls are notoriously unreliable, even being used deceptively to steal food. Africa’s fork-tailed drogos, for example, often use their own, and even other species, <a href="https://www.youtube.com/watch?v=tEYCjJqr21A">vocal alarms</a> to scare competitors away and steal their food.</p>
<p>Non-vocal sounds, by comparison, are unable to be faked. If a crested pigeon flees it cannot help but warn its flock mates, just as it cannot warn its flock mates without fleeing.</p>
<p>This means that these non-vocal alarms are a very reliable indicator of danger – and, more broadly, that non-vocal sounds produced by movement are intrinsically informative and so are likely to evolve for communication.</p>
<h2>Other feathered messages</h2>
<p>Crested pigeons aren’t the only birds that use their feathers to communicate. We know of several other pigeon species that produce conspicuous sounds with their wings that are just waiting to be investigated, such as the Spinifex pigeon.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/193863/original/file-20171108-14193-tqquz4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/193863/original/file-20171108-14193-tqquz4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/193863/original/file-20171108-14193-tqquz4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/193863/original/file-20171108-14193-tqquz4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/193863/original/file-20171108-14193-tqquz4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/193863/original/file-20171108-14193-tqquz4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/193863/original/file-20171108-14193-tqquz4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/193863/original/file-20171108-14193-tqquz4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Spinifex pigeon in the Northern Territory.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/daecks/5837352253/">Flickr/Kristian Golding</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Mourning doves and zenaida doves from the Americas also make sounds, that appear to be produced by their wings, that warn their flock mates of danger.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-research-reveals-the-origin-of-australias-extinct-flightless-giants-the-mihirung-birds-85394">New research reveals the origin of Australia’s extinct flightless giants, the mihirung birds</a>
</strong>
</em>
</p>
<hr>
<p>Non-vocal acoustic signals are used in many other groups to maintain territories and attract mates – manakins and hummingbirds being the most widespread examples.</p>
<p>It appears that non-vocal acoustic communication is much more common than most people thought, and so we hope a new generation of curious people are inspired to listen closely to the animals around them and discover even more of these unusual signals.</p><img src="https://counter.theconversation.com/content/87085/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Trevor Murray works for at the ANU and produced this research as part of their PhD. He received ANU's PhD fellowship funding to undertake this research.</span></em></p>Crested pigeons make a rapid trilling sound when they take flight that can be used to warn others of danger. But what is it that makes the sound?Trevor Murray, Postdoctoral Scientist, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/785292017-06-04T20:22:38Z2017-06-04T20:22:38ZHidden feather patterns tell the story of birds<figure><img src="https://images.theconversation.com/files/171553/original/file-20170531-23707-pmqw5h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Shown as bright orange and pink highlights under X-ray fluorescent light, birds incorporate metals like zinc and bromine into feathers as they grow. </span> <span class="attribution"><a class="source" href="https://www.nature.com/articles/s41598-017-01878-y">Nature Scientific Reports </a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Shearwaters are migratory marine birds that travel in a figure-of-eight pattern between the coasts of Siberia and Japan to Tasmania. </p>
<p>Placing one of the undistinguished grey feathers from a shearwater into the brilliant light of the <a href="http://www.ansto.gov.au/Resources/TEDxSydney/CapabilitiesandInstruments/index.htm">X-ray fluorescence microscopy beam</a> reveals something unexpected. We see intricately patterned deposits of chemical elements that tell the story of how a feather grows. </p>
<p>Among other findings, the images show strikingly regular bands containing zinc. There are roughly the same number of bands as the estimated number of days of feather growth. </p>
<p>Different from simple <a href="https://www.jstor.org/stable/4081089?seq=1#page_scan_tab_contents">feather growth bars</a>, these patterns were not known before <a href="https://www.nature.com/articles/s41598-017-01878-y">our study</a>, published this month. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/171542/original/file-20170530-23672-13khb0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171542/original/file-20170530-23672-13khb0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/171542/original/file-20170530-23672-13khb0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171542/original/file-20170530-23672-13khb0p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171542/original/file-20170530-23672-13khb0p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171542/original/file-20170530-23672-13khb0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171542/original/file-20170530-23672-13khb0p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171542/original/file-20170530-23672-13khb0p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Three breast feathers from three individual Streaked Shearwater birds (<em>Calonectris leucomelas</em>), scanned simultaneously in high resolution X-ray fluorescence microscopy. Regular banding of the element zinc can be seen along the length of the feathers.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41598-017-01878-y/figures/4">Nature Scientific Reports</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Like the annual growth rings of trees, birds’ feathers lay down growth bars during their moult. (Moulting is the process of shedding old feathers, making way for new ones to grow.)</p>
<p>While bars simply show growth, the patterns of chemical elements tell us about the bird’s life during the growth period of the feather. They can indicate environmental exposures in a bird population, perhaps before impacts such as illness and death are clear. </p>
<p>We think the zinc banding may be a natural diurnal (daily) time stamp locked up within the feather. If confirmed, it’s a finding that may be applicable for retrospective dating of the occurrence of stressful events – for example, the temporary exposure to environmental contaminants such as heavy metals – during the period when birds grow new feathers. </p>
<p>In addition to zinc, other elements detected in feathers include calcium, bromine, copper and iron, each with its own unique pattern of distribution. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/171554/original/file-20170531-23653-1dcrxw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171554/original/file-20170531-23653-1dcrxw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/171554/original/file-20170531-23653-1dcrxw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171554/original/file-20170531-23653-1dcrxw5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171554/original/file-20170531-23653-1dcrxw5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171554/original/file-20170531-23653-1dcrxw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171554/original/file-20170531-23653-1dcrxw5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171554/original/file-20170531-23653-1dcrxw5.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">Photographic image [A] and high resolution X-ray fluorescence microscopy images [B-F] in a breast feather from a Flesh-footed Shearwater (<em>Ardenna carneipes</em>); [B] reconstructed Compton scatter (as a density measure) ; [C] calcium distribution; [D] bromium distribution; [E] copper distribution; [F] iron distribution;</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41598-017-01878-y">Nature Scientific Reports</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The team, including field researcher <a href="http://www.utas.edu.au/profiles/staff/imas/Jennifer-Lavers">Jennifer Lavers</a>, analysed feathers painstakingly sampled from remote locations in Japan, as well as Lord Howe Island and New South Wales, and complemented by feathers from the Australia Museum collection in Sydney. </p>
<p>The bulk of the work investigated feathers from three species of shearwaters who migrate more than 60,000km over open ocean each year, to and from their breeding areas.</p>
<p>Foraging across huge areas, shearwaters are important indicators of environmental health. As described by Nobel Laureate and author <a href="https://theconversation.com/peter-doherty-why-our-fine-feathered-friends-deserve-better-7504">Peter Doherty</a> in his book <a href="https://www.mup.com.au/items/118148">Sentinel Chickens</a>: </p>
<blockquote>
<p>Birds of all kinds are recruited by humans to help us interpret changes in our increasingly challenged and unpredictable world. These wonderful creatures continually sample the atmosphere, oceans, fields and forests, signalling toxic and environmental dangers that threaten all vertebrates.</p>
</blockquote>
<p>Studying the population health of our feathered fellow creatures might be translatable into early warning signs for humans.</p>
<p>Observed patterns of chemical elements are also useful in a more fundamental scientific sense, as they open a window onto the dynamics of how feathers grow. It’s an example of “topobiology”, a term that describes the complex growth and regulation processes that take place as a few stem cells develop into an organ or structure such as a feather. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/171547/original/file-20170531-23672-7dc7zk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171547/original/file-20170531-23672-7dc7zk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/171547/original/file-20170531-23672-7dc7zk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=756&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171547/original/file-20170531-23672-7dc7zk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=756&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171547/original/file-20170531-23672-7dc7zk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=756&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171547/original/file-20170531-23672-7dc7zk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=951&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171547/original/file-20170531-23672-7dc7zk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=951&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171547/original/file-20170531-23672-7dc7zk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=951&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Models of pattern formation in feathers. The bands of zinc may be due to mixed stem cells known as ‘follicular cells’ growing feathers over a period of around 30 days [A], or regular systemic pulses of changed zinc concentration [B]</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41598-017-01878-y/figures/2">Nature Scientific Reports</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Developmental biology is usually studied under the highly controlled conditions of a laboratory experiment. However, the current study shows that sensitive markers of development and health can also be applied to samples collected in field studies. </p>
<p>The chemistry of feathers might become a tool for watching our environment.</p><img src="https://counter.theconversation.com/content/78529/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Banati 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>Ordinary grey bird feathers placed under X-ray fluorescence reveal beautiful patterns of elements like zinc, telling a story of feather growth and the environments the birds have experienced.Richard Banati, Chair professor, Australian Nuclear Science and Technology OrganisationLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/617732016-06-29T09:48:53Z2016-06-29T09:48:53ZTiny wings trapped in amber 99 million years ago reveal new secrets of earliest birds<figure><img src="https://images.theconversation.com/files/128559/original/image-20160628-7832-evjbo.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Royal Saskatchewan Museum/RC McKellar</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Fossilised amber is like a time capsule, a snapshot into a world millions of years old, and ancient creatures discovered in this amber give us fascinating insights into the past. </p>
<p>The amber deposits of north-east Myanmar (Burma) have become famous for thousands of fossils that preserve an astonishing array of plants, insects, spiders, scorpions and lizards from the Cretaceous period that were unfortunate enough to become trapped in the sticky sap of ancient trees – sap which over millions of years becomes amber. Rarely, collectors have found isolated feathers, and even more rarely parts of ancient birds. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/128555/original/image-20160628-7840-uahzv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/128555/original/image-20160628-7840-uahzv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/128555/original/image-20160628-7840-uahzv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/128555/original/image-20160628-7840-uahzv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/128555/original/image-20160628-7840-uahzv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/128555/original/image-20160628-7840-uahzv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/128555/original/image-20160628-7840-uahzv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/128555/original/image-20160628-7840-uahzv.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"></a>
<figcaption>
<span class="caption">Fossils of the early bird <em>Confuciusornis sanctus</em> from the Jehol group.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Confuciusornis_sanctus.jpg">Edward Sola</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Xing Lida from the China University of Geosciences in Beijing, together with a large team including myself, are among those to make such a rare discovery: two tiny fossil wings preserved complete with feathers, as detailed <a href="http://nature.com/articles/doi:10.1038/ncomms12089">in a paper</a> published in Nature Communications.</p>
<p>Unlike the even more famous <a href="http://palaeo.gly.bris.ac.uk/melanosomes/jehol.html">fossil birds from the Jehol Group</a> of north-east China that are preserved only as imprints in stone, these Burmese fossils are three-dimensional, the first ever discovery of not only the bony skeleton of the wing, but also the feathers in their original arrangement and even the underlying skin.</p>
<p>The two wing fragments from two juveniles of the earliest types of birds are each only around one centimetre long, but following CT scanning the bones are clearly visible. Attached to the back of the ulna and metacarpals – the bones that would in a human be the forearm and fingers – are nine primary and five secondary flight feathers, evenly spaced, and in their original positions. These feathers are asymmetrical, with a vane (the feather’s body) of unequal size to either side of the quill, the feather’s central shaft. This asymmetry is usually interpreted as evidence that the feathers were used in flight.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/128562/original/image-20160628-7825-s2wqdc.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/128562/original/image-20160628-7825-s2wqdc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/128562/original/image-20160628-7825-s2wqdc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/128562/original/image-20160628-7825-s2wqdc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/128562/original/image-20160628-7825-s2wqdc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/128562/original/image-20160628-7825-s2wqdc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/128562/original/image-20160628-7825-s2wqdc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/128562/original/image-20160628-7825-s2wqdc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Close-up of the wing showing the feathers’ barbs and barbules.</span>
<span class="attribution"><span class="source">Royal Saskatchewan Museum/RC McKellar</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Just as with feathers from modern birds, when examined in detail the feathers reveal barbs – the ridged formations on a bird’s feathers – and barbules – tiny hooks on the barbs – that allow the separate feathers to “zip” closely together to form a continuous flight surface so the bird can fly. It also enables ruffled feathers to be preened and smoothed back into shape. There are even visible traces of plumage colour – light and dark patches – but it’s impossible to explore the chemistry and potential original colours while the feathers are entirely encased in amber.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/128563/original/image-20160628-7851-dsttr5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/128563/original/image-20160628-7851-dsttr5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/128563/original/image-20160628-7851-dsttr5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/128563/original/image-20160628-7851-dsttr5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/128563/original/image-20160628-7851-dsttr5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=590&fit=crop&dpr=1 754w, https://images.theconversation.com/files/128563/original/image-20160628-7851-dsttr5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=590&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/128563/original/image-20160628-7851-dsttr5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=590&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ultraviolet light reveals the direction of flow of the amber.</span>
<span class="attribution"><span class="source">Royal Saskatchewan Museum/RC McKellar</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The anatomy of the bones shows that both specimens belong to enantiornithines, a group of birds that dominated the skies in the Cretaceous period, but died out during the same great mass extinction that killed off the dinosaurs 66m years ago. These are early birds, so they still had three fully-formed fingers with claws, like their dinosaurian ancestors, that could grasp branches in order to climb trees. In comparison, modern birds retain the three fingers, but they cannot grasp and have lost the claws.</p>
<p>The specimens also tell us something of the moment these birds met their fate: small scratch marks visible in the amber suggest one of the little birds was scrabbling to free itself. The fact that only one wing is preserved in each case perhaps tells us something too: we can assume these tiny birds, each with stumpy wings that are little larger than a man’s thumbnail, were clambering about on tree branches perhaps in search of insects or fruit to eat. They blundered into the tree sap and their feathers became entangled. The more they struggled, the more their feathers became stuck, and as the amber hardened they could not escape. The rest of their bodies decayed and fell away, leaving just two pristine little wings preserved forever.</p>
<p>Apart from this vivid vignette of life and death 99m years ago, these wings offer the hope of more such discoveries. When the Jehol birds were found in China in the 1990s, they revolutionised our understanding of the early history of birds. The chance of finding feathers and soft tissues from these times means palaeontologists can flesh out more details in their understanding of the earliest birds. This is important: birds today are one of the most successful groups of animals with 10,000 species. In terms of biodiversity and conservation of these species, we need to know why they are so successful.</p><img src="https://counter.theconversation.com/content/61773/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Benton receives funding from NERC and the Leverhulme Trust. </span></em></p>For the first time, feathers, bone and skin of the earliest birds have been found, trapped in amber.Michael J. Benton, Professor of Vertebrate Palaeontology, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/570442016-04-15T02:00:40Z2016-04-15T02:00:40ZAustralia’s waterbirds are disappearing – but nuclear physics can help save them<figure><img src="https://images.theconversation.com/files/118236/original/image-20160412-21989-1nowvr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Straw-necked ibis gather to breed. </span> <span class="attribution"><span class="source">Kate Brandis</span>, <span class="license">Author provided</span></span></figcaption></figure><p>When wetlands flood they become full of life. They are spectacularly beautiful and noisy. There is nothing quite like the sound of a wetland when thousands of birds come together to take advantage of the newly created habitat.</p>
<p>Ibis, spoonbills, egrets, herons, cormorants and pelicans all congregate in large numbers, tens to hundreds of thousands, to breed when wetland conditions are good. These gatherings of birds are spectacular, but a mystery remains: where do they come from, and where do they go?</p>
<p>These questions aren’t trivial. <a href="https://www.ecosystem.unsw.edu.au/content/rivers-and-wetlands/waterbirds/eastern-australian-waterbird-survey">Over the past 30 years waterbird populations have declined</a> as opportunities for breeding have disappeared, mainly <a href="http://www.sciencedirect.com/science/article/pii/S0006320708000451">due to water resource development</a>. </p>
<p>Worldwide, wetlands have been lost or are under threat from water resource development, agricultural development and climate change. In Australia we have <a href="http://link.springer.com/article/10.1023%2FA%3A1008495619951#page-1">lost an estimated 50% of wetlands since European settlement</a>. </p>
<p>The loss of wetlands has serious implications for wildlife. Many species are wetland-dependent throughout their lives while others, such as some species of waterbirds, rely on wetlands as places to breed.</p>
<p>Knowing which wetlands waterbirds use when they aren’t breeding will help us figure out which places we need to protect. So the Centre for Ecosystem Science, UNSW and the Australian Nuclear Science Technology Organisation have developed a new technique to analyse Australian bird feathers using nuclear physics. </p>
<p>Now we want you to <a href="http://feathermap.ansto.gov.au/">send us waterbird feathers</a> so we can build an Australia-wide map of where our waterbirds go. </p>
<h2>High-tech tracking</h2>
<p>Traditional tracking methods such as leg banding and satellite trackers have had limited success and can be expensive. So we looked for a cheaper and more effective method. And what could be easier than collecting bird feathers? </p>
<p>Feathers are made of keratin (the same material as human hair and nails) and as they grow record the diet of the bird in chemical elements. Once fully grown, feathers are inert – they no longer change. </p>
<p>Chemical elements (carbon, nitrogen, hydrogen, oxygen) exist in a number of different forms known as isotopes. Some isotopes of some elements are radioactive, but many elements have stable, non-radioactive isotopes. The relative proportion of different isotopes can be <a href="http://www.pnas.org/content/95/26/15436.full">explicitly linked to a specific location</a>, as has been done for monarch butterflies in North America.</p>
<p>To test whether this could be applied to Australian wetlands and waterbirds I did a pilot study in 2010-11. Widespread flooding in the Murray-Darling Basin resulted in colonial waterbirds breeding at a number of wetlands including the Gwydir wetlands, Macquarie Marshes and Lowbidgee wetlands. These three wetlands are geographically distinct, spread across the Basin from north to south. </p>
<iframe src="https://www.google.com/maps/d/u/0/embed?mid=zXUWIAKxCpHk.kEeaM7o1lrDI" width="100%" height="480"></iframe>
<p>We used feathers from chicks and juveniles, because they are eating food from only the wetland where they were hatched and so provide a unique signature for that wetland. </p>
<p>We tested the feathers using two techniques: one to look at the elemental composition of feathers, and the other to measure the amount of two particular isotopes, carbon-13 and nitrogen-15.</p>
<p>Results from these analyses showed that we were able to distinguish between the three wetland sites based on the elemental composition of the feather and the isotopic composition. </p>
<p>Either technique showed the ability to distinguish between wetland sites. Combined, they should be able to provide greater spatial accuracy in identifying the wetland at which the feather was grown. With the knowledge that wetlands have their own unique elemental and isotopic signature, we are expanding the study nationally. </p>
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<a href="https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/118237/original/image-20160412-21989-1l2w9sl.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">Sunset at an ibis colony.</span>
<span class="attribution"><span class="source">Kate Brandis</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Building a ‘feather map’</h2>
<p>The Feather Map of Australia is a citizen science project that aims to map the signatures for as many wetlands across Australia as possible. To do this we have asked interested members of the public to collect feathers from their local wetlands and contribute them for analyses. </p>
<p>Once analysed, we will have an isotopic map of wetlands against which we can track waterbird movements. Feathers collected from chicks and birds that don’t move large distances will provide us with a signature for that particular wetland. We can then analyse the feathers of birds that do travel long distances and match the signature in their feathers against those of wetlands, telling us where these birds have been. </p>
<p>The signature will not tell us all the movements a bird has made, but it will tell us where it was when it grew the feather. And this will also give us information about the health of the wetland based on what food the bird has eaten and how long it took to grow the feather.</p>
<p>Knowing the movements of waterbirds helps identify wetlands that are important waterbird habitats. This knowledge can be used to provide information to policymakers and land and water managers for improved water delivery, wetland management and decision-making, and ultimately protect wetlands and waterbirds. </p>
<p><em>Read more on how to <a href="http://feathermap.ansto.gov.au/GetInvolved/index.htm">send feathers to scientists</a> and help build the Feather Map of Australia.</em></p><img src="https://counter.theconversation.com/content/57044/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kate Brandis receives funding from Australia Nuclear Science Technology Organistion and the UNSW.</span></em></p>Bird feathers can tell us a lot about their owners and the places they visit.Kate Brandis, Joint Research Fellow, Centre for Ecosystem Science, UNSW and Australia Nuclear Science Technology Organisation, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.