Eastern Screech-Owl

Megascops asio

Illustration by Donald L. Malick

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In eastern wooded suburbs, this small, owl is often the most common avian predator, emerging from its nest or roost hole at dusk to hawk insects or hunt other small prey, including songbirds and rodents. Its whinnying and trilling songs are familiar, but its vocalizations also include rasps, barks, hoots, chuckles, and screeches. Its hunting is mostly nocturnal but often crepuscular and occasionally diurnal; it nests in old woodpecker holes or natural tree cavities and readily uses properly sized and positioned nest boxes. Courtship occurs late January through mid-March, with the male advertising its presence and also potential nest sites. Eggs are laid beginning in early March; fledging begins mid- to late May. The juvenile remains dependent on parents for another 8 to 10 weeks. The eastern was formerly classified with the western as a single species; range separation is not yet fully known. Polytypic (5–6 ssp.; all in North America). Length 8.5" (22 cm); wingspan 21" (53 cm).

Identification Adult: small; yellow eyes; bill yellow-green at the base with a paler tip. Ear tufts are prominent if raised; when flattened the bird has a round-headed look. Facial disk is prominently rimmed dark, especially on the lower half. Underparts are marked by vertical streaks crossed by widely spaced dark bars that are nearly as wide as the streaks. Scapulars have blackish edged white outer webs, forming a line of white spots across the shoulder. Feet are proportionately large. Occurs in rufous and gray morphs as well as intermediate brownish plumages; plumages are alike, but the female is larger. Markings on underparts are less distinct on rufous morph birds. Juvenile: similar to adult in coloration, but indistinctly barred light and dark on head, mantle, and underparts; ear tufts not yet fully developed.

Geographic Variation Body size and intensity of markings vary clinally: smaller and darker in the south and east, larger and lighter in the north and west. Color morph distribution is more complex. In most areas intermediate brownish birds compose less than 10 percent of the population; but in Florida, gray, rufous, and brownish birds are evidently about equally common. The rufous morph becomes more common in the Southeast and outnumbers the gray morph in some areas. Normally only gray morph birds are found on the Great Plains and in southernmost Texas. The large northwest subspecies maxwelliae is the palest and most faintly marked.

Similar Species The western screech-owl’s bill is blackish or dark gray at the base, but gray-plumaged individuals are otherwise nearly identical in appearance and habits to the Eastern gray morph birds. Where their ranges overlap, the two species are best identified by voice.

Voice The territorial defense song is a strongly descending and quavering trill up to 3 seconds long, reminiscent of a horse’s whinny. The contact song (3–6 secs.) is a single low-pitched quavering trill of about 14 notes per second that may rise or fall slightly at the end. The male utters this sound when advertising a nest site, courting, and arriving at the nest with food. Both sexes sing each song; the female’s voice is slightly higher pitched. Both adult females (during courtship) and juveniles beg for food with a rough, grating rasp, usually falling in pitch.

Status and Distribution Common. Range now overlaps that of the western screech-owl in eastern Colorado, along the Cimarron River, in extreme southwest Kansas, and in Texas east of the Pecos River to near San Angelo. Both species are found at Big Bend National Park in Texas, where the western is uncommon and the eastern is rare; hybrids are known from there and from eastern Colorado. Year-round: resident in a wide variety of tree-dominated habitats: woodlots, forests, river valleys, swamps, orchards, parks, suburban gardens below about 4,500 feet. May make local or altitudinal movements in severe winters or during food shortages.

Population Generally thought to be stable.

—From the National Geographic book Complete Birds of North America, 2006

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