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Eastern Screech-Owl
Megascops asio
Order
STRIGIFORMES
– Family
STRIGIDAE
Authors: Gehlbach, Frederick R.

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Introduction

Gray-morph Eastern Screech-Owl roosting in cavity, Tompkins Co, NY, October.
Figure 1. Distribution of the Eastern Screech-Owl.

The Eastern Screech-Owl has the broadest ecological niche of any owl in its range. It occurs east of the Rocky Mountains, where it is a permanent resident of both rural and urban habitats from south of the Canadian boreal forest to near the Tropic of Cancer in Mexico. This species nests in tree cavities in wooded environments below about 1,500 meters, regardless of habitat, occupying lowland forests to mountainside woodlands, both deciduous and evergreen. Because it readily habituates to people, this species sometimes nests in human-made cavities such as bird boxes. It is often the most common or only avian predator in wooded suburban and urban habitats.

Eastern Screech-Owls are monogamous and polygynous, forming pairs of same-age individuals in small territories around alternative nest sites. Nesting occurs between March and June. Adults incubate their three to four eggs for thirty days, feed the nestlings for nearly as long, and then tend the fledglings for eight to ten weeks. Foods include terrestrial and aquatic invertebrates and vertebrates taken opportunistically; the diet is the most varied of any North American owl. The monotonic and descending trill songs of this owl are familiar and are often used for ambience in television and movie night scenes, but the species’ vocal repertoire also includes various barks, hoots, rasps, chuckles, 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), the species resembles and is closely related to the Western Screech-Owl (Megascops kennicottii), from which it is distinguished by its descending trill, yellowish bill, and in some individuals, rufous coloration.

Although the Eastern Screech-Owl is one of our most familiar North American birds, it is poorly studied. Only central Texas populations are known with respect to integrated features of life history, behavior, and ecology. One other long-term investigation of population dynamics has been conducted in northern Ohio. Both studies used nest boxes, which facilitate making observations and provide reliable information about breeding.

Unless otherwise indicated, numerical values in this account are averages.