They're one of the only bird species to do this. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. Researchers have cracked the case of why ...

A new analysis of old data suggests that the endangered erect-crested penguin's bizarre nesting habits -- rejecting the first egg they lay -- is because they can't feed two chicks, and the second, ...

Q. When we studied high school biology, our teacher said more than 99% of animals lay eggs and only a few give live birth. That percentage seems too high. Humans, dogs, cats and cows are ...