Smallest organisms
With a mass of approximately and a length of 5 centimetres (2.0 in), the bee hummingbird ("Mellisuga helenae") is the world's smallest bird species and the smallest warm-blooded vertebrate. Called the "zunzún" in its native habitat on Cuba, it is lighter than a Canadian or U.S. penny. It is said that it is "more apt to be mistaken for a bee than a bird". The bee hummingbird eats half its total body mass and drinks eight times its total body mass each day. Its nest is 3 cm across.
Elf owl
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. It is also the world's smallest owl. The mean body weight of this species is . These tiny owls are long and have a wingspan of about . 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.