The elf owl (Micrathene whitneyi) is a member of the owl family Strigidae, that breeds in the southwestern United States and Mexico. It is the world's lightest owl, although the long-whiskered owlet and the Tamaulipas pygmy owl are of a similarly diminutive length. The mean body weight of this species is 40 grams (1.4 ounces). These tiny owls are 12.5 to 14.5 centimetres (4.9 to 5.7 in) long and have a wingspan of about 27 cm (10.5 in). Their primary projection extends nearly past their tail. They have fairly long legs and often appear bow-legged. They can often be heard calling to one another just after dusk or at sunset. Their call is a high-pitched whinny or chuckle. The male and female dart around trees and call back and forth.