Elf owls are roughly fourteen centimetres long and weigh around 35 to 50 grams, the lightest of all owls. They cannot excavate, so they depend on holes made by gila woodpeckers and gilded flickers in saguaro and in riparian trees.
The cactus makes the arrangement work. When a saguaro is drilled it walls off the wound with a tough internal lining, and the resulting cavity is measurably cooler than the desert air outside and difficult for most predators to reach. Elf owls also use holes in sycamores, oaks and utility poles where cactus is absent.
Diet is almost entirely invertebrate: moths, beetles, crickets and scorpions, with the scorpion's sting usually removed before the prey is swallowed or delivered to the young. Northern populations are migratory, leaving the United States in autumn, which is often overlooked in accounts that treat the species as a permanent desert resident.