CHICAGO — It’s springtime, and the birds are chirping as they begin to build their nests. Researchers say the hands-on clock is turning back, though it happens like clockwork each year. Many species ...

"It's hard not to feel like a proud parent seeing them out there thriving and making history," London Zoo bird keeper Charlotte James said Jonny Shepherd/TNC-ZSL; TNC-ZSL The once-extinct Sihek bird ...

Q. I saw a photo of different kinds of bird eggs and noted not only the obvious, that smaller birds lay smaller eggs, but also that some bird eggs are elongate whereas others are more rounded. What is ...

The number of eggs a bird lays — its clutch size — varies greatly among species. You might think every species should simply lay lots of eggs because that would increase the odds of more young birds ...

Q. I saw a photo of different kinds of bird eggs and noted not only the obvious, that smaller birds lay smaller eggs, but also that some bird eggs are elongate, whereas others are more rounded. What ...