Birds spend a lot of time and energy singing, but they don’t do it the same way in every season of the year. And some can’t sing at all. What’s the purpose of birdsong?
Even in the breeding grounds, we found that European bee-eaters preferred the company of some birds over others. These tended to be the individuals they migrated with.
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.
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.
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.
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.
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.