Burrowing owls are unlike other owls in almost every way: they live underground, not in trees; they are active during the day, not at night; and they live in colonies. These unusual owls also line their nests with the dung of cows, horses and other mammals. But until a study published this year, scientists didn't have a clear idea why they practice this smelly behavior. Turns out the feces-decorated homes tended to attract more insects for the owls to eat.