The elf owl (Micrathene whitneyi) is a small grayish-brown owl about the size of a sparrow found in the Southwestern United States, central Mexico, and the Baja California peninsula. It has pale yellow eyes highlighted by thin white "eyebrows" and a gray bill with a horn-colored tip. The elf owl frequently inhabits woodpecker holes in saguaro cacti; it also nests in natural tree cavities. It is nocturnal and feeds primarily on insects. Taxonomy The elf owl was formally described in 1861 by the American naturalist James Graham Cooper from a specimen collected near Fort Mohave in Arizona. He coined the binomial name Athene whitneyi, choosing the specific epithet to honour the geologist Josiah Whitney. The owl is now the only species placed in the genus Micrathene that was introduced in 1866 specifically for the elf owl by American ornithologist Elliott Coues. The genus name combines the Ancient Greek mikros meaning "small" and the genus name Athene that had been introduced by Friedrich Boie in 1822. A molecular phylogenetic study of the owls published in 2019 found that the elf owl is a sister species to the South American long-whiskered owlet (Xenoglaux loweryi) that was first described in 1977. Four subspecies are recognized: M. w. whitneyi (Cooper, JG, 1861) – southwest USA and northwest Mexico M. w. idonea (Ridgway, 1914) – south Texas (USA) to central Mexico M. w. sanfordi (Ridgway, 1914) – south Baja California (Mexico) † M. w. graysoni Ridgway, 1886 – Socorro Island (off west Mexico) (extinct) M. w. idonea, the subspecies in southernmost Texas to central Mexico, is resident, as are the isolated M. w. sanfordi of southernmost Baja California and M. w. graysoni (Socorro elf owl) of Socorro Island, southwest from the tip of Baja California. The Socorro elf owl has not been recorded since 1931 and is assumed to be extinct. Description The elf owl 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 (flight feather) extends nearly past their tail. They have fairly long legs and often appear bow-legged. They are often found in chaparral, and are easily found during their breeding season. During dusk and just before dawn are the times