One of North America's smallest owls, the Northern Pygmy-Owl is reputed to be a fierce and bold hunter. Bent ( Bent 1938b ) referred to it as “blood-thirsty, rapacious . . . fiend . . . from the top of its gory beak to the tips of its needle-like-claws.” Old beliefs die hard; this owl's habit of killing passerines, often at bird feeders, does not help its reputation even today.
Despite this bird's broad geographic distribution in western North America, it is one of the least studied owls on the continent. Its habitats range from deciduous bottomlands to high-elevation coniferous forests. Rarely seen during the breeding season, it is more commonly observed during the nonbreeding season as individuals move into towns and hunt birds and small mammals during the day—often taking birds at feeders. True migration is not yet known for this species. Much of its diet consists of small birds and mammals, although insects may also be important during the breeding season. It nests in cavities, both natural ones and those excavated by woodpeckers.
Plumage coloration and pattern resembling false eyes or a false face on the back of the head are distinctive features of this owl. Its toot-like song can be heard year-round and appears to have several functions.
The taxonomy of pygmy-owls (Glaucidium spp.) is controversial and unresolved; as traditionally classified, for example, Northern Pygmy-Owl may include two or more species. Differences in the Primary Song, augmented by molecular data and ecological differences, may provide clues to resolve the relationships within this complicated group of birds.
The Northern Pygmy-Owl has been little studied. Observations made by Holman ( Holman 1926 ) in California detail some aspects of breeding biology. In Montana, breeding season observations made by Norton and Holt ( Norton and Holt 1982 ) and Holt and Norton ( Holt and Norton 1986 ) describe breeding biology, diet, and habitat. Other Montana data reported by Holt and Leroux ( Holt and Leroux 1996 ) detail Northern Pygmy-Owl feeding ecology. Giese ( Giese 1999 ) provides information on habitat selection, diet, and territory size in Washington State.