Yolks are a great source of vitamins, minerals, fats and proteins packaged up by the female animal for an embryo.
Emily Nunell/The Conversation CC-NY-BD
A yolk allows a developing animal to stay in an egg longer, boosting its chance of survival. The downside is the mother has to work hard finding extra food so her body can create a nutritious yolk.
The SeaGen tidal generator in Northern Ireland leaves turbulent water – and lots of fish – in its wake.
Alex Nimmo Smith
New research finds birds like to forage for fish in the wake of a tidal power plant.
Chicken or rooster? This bird is both – female on the left (dark feathers), and male on the right (white feathers, with larger comb and physique).
Mike Clinton (Roslin Institute)
Birds have some of the most amazing sex differences of any animal. They can control the sex of offspring, and even produce rare half-male, half-females. And their sex genes and chromosomes are quite different from ours.
Osprey on a nesting platform in Massachusetts.
Chemical pollution and hunting pushed Ospreys to the edge of extinction in the mid-20th century. Today, they have rebounded and can be spotted worldwide, often nesting on manmade structures.
Male collared flycatcher, singing for multiple females.
Biologists investigated whether birds that search for multiple mates would evolve ever more elaborate songs to attract them. What they found might have surprised Darwin.
Menno Schaefer / shutterstock
The birds follow a few simple rules to create complex patterns.
A red-listed skylark.
One gram of songbird meat is estimated to sell for the equivalent of one gram of marijuana.
Nowhere for wildlife to Hyde.
I Wei Huang/Shutterstock
Keeping urban habitats such as parks neat and tidy by removing dead wood and leaves is driving the species which live there to extinction.
Robins are a much loved Christmas icon, but wind turbines installed in their habitat are affecting their song, with worrying consequences.
Do you know this downy woodpecker?
By looking closely at traits like wing feathers and spot patterns, a computer scientist trained an algorithm to recognize individual woodpeckers.
A pink pigeon in the wild of Mauritius.
Pink pigeons may make more charismatic subjects for our adoration, but their feral relatives who keep us company in towns and cities are just as deserving.
Generations of giraffes.
It can actually be very tricky to define a species, but in the 1900s, scientists found a pretty good way.
Success with conservation of Kangaroo Island’s Glossy Black-Cockatoos can now be compared with other bird conservation efforts around the country.
New research has shown how to measure conservation progress for Australia's 238 endangered bird species
Gyps fulvus gliding out from les Rocher des Aigles ornithological centre, France, carrying bio-logging tag.
Even when birds are not flying in a flock, they may observe each other to sense the world around them.
Zhao Chuang and PNSO
A new type of Archaeopteryx fossil helps build the case for this creature being called 'the first bird'.
The composition of black and white in a magpie’s poo differs between species. Some splatter more of the uric acid (white), some have more black (indigestible solids). It depends on their diet.
Like reptiles, birds do not have two separate exits from the body. They have one, called the cloaca. It is quite similar to the human anus but the cloaca expels both indigestible bits and toxins.
On the fence.
As both beneficiary and victim of EU policies, yellowhammers are apt symbols for Brexit's divisions.
The majestic White Ibis.
The ibis has become an Australian cultural phenomenon. The birds' tenacity and fearlessness as environmental refugees mean they attract love and hate alike.
Not all birds have eyes on the sides of their heads – but even those that do can see straight in front of them.
Could music one day be something we experience through augmented reality, responding to the way we move through the world? Sound supplemented with colours and shapes?
Mavis Wong/The Conversation NY-BD-CC
Today, we're hearing about a researcher who records birdsong, how tech changes music and why song might help address Indigenous language loss.