Run-of-the-mill city pigeons, known as rock doves, build their nests in the nooks and crannies of the concrete cityscape, reminiscent of their native European and Middle Eastern cliffside habitats. Parents typically keep babies, or squabs, hidden and safe until they can survive on their own, usually a month after hatching.

As a result, youngsters are almost fully grown and their feather coloring looks nearly identical to an adults by the time they fly the coop, says Karen Purcell, who leads Cornell Universitys Project PigeonWatch, a grassroots study of feather colorings.

Carnivorous plants generally stick to a diet of bugs that they ensnare. On rare occasions, though, tropical pitcher plants—which drown and break down prey in vase-shaped traps that can be smaller than a little finger or larger than a football—have been found holding the skeletal remains of frogs, geckos and even small rodents. But what about human flesh?