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 ...

Fork-tailed drongos have a signature color and pattern on their eggs, which helps them avoid getting duped by African cuckoos. Hans Stieglitz via Wikimedia Commons under CC BY-SA 3.0 Cuckoos have ...

Across the animal kingdom, eggs can appear green, brown, pink, and even bright blue depending on the species that lays them.

Female lineages of European cuckoos lay eggs with colorful shells and intricate patterns specialized to deceive more than 100 avian hosts into fostering their chicks. Parasitic cuckoo eggshells show ...

Black birds with a greenish sheen and brown heads sometimes visit my yard during spring migration. These are male brown-headed cowbirds, and they often arrive in mixed flocks of red-winged blackbirds ...

You wake up, head out to check your mail, and see a collection of small, strange eggs nestled in the grass. Are you looking at a clutch of snake or bird eggs? The clues as to whether the eggs are the ...

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 ...