What really came first -- the chicken or the egg? Birds' reproductive biology is dramatically different from that of any other living vertebrates, and scientists have long wondered how and when the ...

Fossil by fossil, paleontologists have traced birds back to their dinosaur ancestors. As they’ve done so, traits once thought to be distinct characteristics of avians – such as feathers and air sacs – ...

As winged dinosaurs underwent a series of evolutionary changes during the transition into Aves, or birds, one pivotal transformation was the appearance of a single-ovary reproductive system. "The most ...

CHAMPAIGN, Ill. — A new study reported in the Proceedings of the National Academy of Sciences assessed changes in the reproductive output of 104 bird species around the world between 1970 and 2019.