The Sonoran desert of southern Arizona is where you'll find those huge, iconic saguaro cacti, some as tall as 40 feet (12 meters). Giant saguaro serve as high-rise apartment buildings for elf owls (Micrathene whitneyi), the world's smallest, which make their homes in abandoned woodpecker nest cavities carved out of the cactus flesh. High off the ground and insulated by the saguaro's thick walls, elf owls and their young are relatively safe from predators and protected from extreme temperatures.

Tiny elf owls are the size of a sparrow and weigh between 1 and 2 ounces (0.02 and 0.05 kilograms), or less than a golf ball. Their feathers are grayish to brownish (good colors for desert camouflage), and they have large, pale yellow eyes in a round head without the usual ear tufts of other owls. Long legs help them chase prey on the ground; when perched, they look bowlegged, like the world's smallest cowboys. If that isn't cute enough, their calls sound like a puppy yipping.

Elf owls hunt at dusk and during the night for insects and the occasional scorpion (eaten after the stinger is carefully removed). No need for water in this dry landscape; elf owls get all they need from their prey. Like other owls, elf owls are silent but deadly. Usually, air flow over bird wings makes a gushing sound. But owl wings have little projections on the front edge and a fringe of feathers at the back edge that break up air flow and reduce sound. Almost all remaining noise is absorbed by soft feathers on the wings and legs. Critters don't know what's coming for them until it's too late.

In the spring, females lay one to four eggs, which hatch in around three weeks. At first dad brings food back for mom and chicks, then after a few weeks mom also hunts for food to satisfy the growing brood. After the babies have fledged and when nights get cooler and tasty bugs harder to find, elf owls make their way down to Mexico and Central America to spend the winter.

Elf owls would rather flee than fight, but they have been known to mob predators like great horned owls. Making loud alarm calls, a few elf owls dive-bomb the larger owl, then more birds join in, sometimes of different species. Its cover blown, the great horned owl's chance of catching an elf owl dinner takes a nosedive too. If a predator manages to get close, elf owls have another trick: playing dead until the danger has passed.