Ritchison, Gary, Frederick R. Gehlbach, Peter Pyle and Michael A. Patten.(2017).Eastern Screech-Owl (Megascops asio), The Birds of North America (P. G. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology
Eastern Screech-Owl (Megascops asio)
The Eastern Screech-Owl has the broadest ecological niche of any owl in its range. They occur east of the Rocky Mountains, where they are permanent residents of both rural and urban habitats from south of the Canadian boreal forest to near the Tropic of Cancer in Mexico. These owls nest in tree cavities in wooded environments below about 1,500 meters, occupying lowland forests to mountainside woodlands, both deciduous and evergreen. Because they readily habituate to people, Eastern Screech-Owls sometimes roost and nest in human-made cavities such as bird boxes. They are often the most common avian predator in wooded suburban and urban habitats. Eastern Screech-Owls are socially and genetically monogamous. Nesting occurs between March and June. Females incubate 3 to 5 eggs for 30 days, feed nestlings for nearly as long, and then tend the fledglings for 8 to 10 weeks. Prey include terrestrial and aquatic invertebrates and vertebrates taken opportunistically; their diet is the most varied of any North American owl. The monotonic trill and whinny call of Eastern Screech-Owls are their most frequent vocalizations, particularly in the weeks before nesting begins when pairs are forming and during late summer and early fall when young are dispersing and seeking their own territories, but their vocal repertoire also includes various barks, hoots, squeals, and screeches—hence the common name. The Eastern Screech-Owl has two color-morphs, rufous and gray. No other North American owl has such distinctive plumage differences. In size (and in gray plumage), this species resembles and is closely related to the Western Screech-Owl (Megascops kennicottii), from which they are distinguished by their descending trill, pale yellowish-green or pale gray bill and, in some individuals, rufous coloration.