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Eastern Screech Owl
Image-1466794688
Grey morph
Information
Common Name Eastern Screech-owl
Range Eastern orth America, from Mexico to Canada.
Scientific Classification
Kingdom Animalia
Phylum Chordata
Class Aves
Order Strigiformes
Family Strigidae
Genus Megascops
Species Megascops asio
Conservation Status
LCSpecies
Least Concern

The Eastern screech owl or eastern screech-owl (Megascops asio), is a species of screech owl that is relatively common in Eastern North America, from Mexico to Canada. This species is native to most wooded environments of its distribution and, more so than any other owl in its range, has adapted well to manmade development, although it frequently avoids detection due to its strictly nocturnal habits.

Description

Adults range from 16 to 25 cm (6.3 to 9.8 in) in length and weigh 121–244 g (4.3–8.6 oz). Among the differently sized races, length can average from 19.5 to 23.8 cm (7.7 to 9.4 in). The wingspan can range from 46 to 61 cm (18 to 24 in). In Ohio, male owls average 166 g (5.9 oz) and females 194 g (6.8 oz) while in central Texas, they average 157 g (5.5 oz) and 185 g (6.5 oz), respectively. They have either rusty or dark gray intricately patterned plumage with streaking on the underparts. Mid-sized by screech-owl standards, these birds are stocky, short-tailed (tail averages from 6.6 to 8.6 cm (2.6 to 3.4 in) in length) and broad-winged (wing chord averages from 14.5 to 17 cm (5.7 to 6.7 in) as is typical of the genus. They have a large round head with prominent ear tufts, yellow eyes and a yellowish beak, which measures on average 1.45 cm (0.57 in) in length. The feet are relatively large and powerful compared to more southern screech owls and are typically feathered down to the toes, although the southernmost populations only have remnant bristles rather than full feathering on the legs and feet. The eastern screech owl (and its western counterpart) are actually one of the heaviest screech owls, the largest tropical screech owls do not exceed them in average or maximal weight but (thanks to the eastern screech owls' relatively short tail) they are surpassed in length by Balsas (Megascops seductus), long-tufted (Megascops sanctaecatarinae), white-throated (Megascops albogularis) and rufescent (Megascops seductus), in roughly that order.

Two color variations are referred to as "red or rufous morphs" and "gray morphs" by bird watchers and ornithologists. Rusty birds are more common in the southern parts of the range; pairings of the two color variants do occur. While the gray morph provides remarkably effective camouflage amongst the bark of hardwood trees, red morphs may find security in certain pine trees and the colorful leaves of changing deciduous trees. The highest percentage of red morph are known from Tennessee (79% of population) and Illinois (78% of population). A rarer "brown morph" is known, recorded exclusively in the south (i.e. Florida), which may be the occasional product of hybridation between the morphs. In the state of Florida, brown morphs are typically reported in the more humid portions of the state, whereas they appear to be generally absent in the northern and northwestern parts of the state. A paler gray variation (sometimes bordering on a washed-out, whitish look) also exists in western Canada and the north-central United States.

Confusion with Other Species

In the closely related western screech owl (Megascops kennicottii), there are not "morphs", as all owls of the western species are gray. Besides coloration, the western screech owl is of almost exactly the same general appearance and size as the eastern. The only reliable distinguishing features are the bill color, which is considerably darker (often a black-gray) in the western and olive-yellow in the eastern, and their different voices. The eastern and western screech owls overlap in the range in the Rio Grande valley at the Texas-Mexico border and the riparian woods of the Cimarron tributary of the Arkansas River on the edge of southern Great Plains. Other somewhat similar species that may abut the eastern screech owl's range in its western and southernmost distribution, like the Middle American screech owl (Megascops guatemalae; formerly called "vermiculated screech owl"), whiskered screech owl (Megascops trichopsis) and the flammulated owl (Psiloscops flammeolus), are distinguished by their increasingly smaller body and foot size, different streaking pattern on breast (bolder on the whiskered, weaker on the others), different bare part coloration, and distinctive voices. Through much of the eastern United States, eastern screech owls are essentially physically unmistakable, because other owls with ear tufts are much larger and different colored and the only other small owl, the northern saw-whet owl (Aegolius acadius) is even smaller, with no ear tufts, a more defined facial disc, and browner overall color

Subspecies

Five subspecies are typically treated for the eastern screech owl but the taxonomy in the species is considered "muddled". Much of the variation may be considered clinal, as predictably, the size tends to decrease from north to south and much of the color variation is explainable by adaptation to habitat:

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Name
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Megascops asio asio

(Linnaeus, 1758)

Includes previously described races no longer considered valid such as Megascops asio carolinensis, Megascops asio naevius and Megascops asio striatus. Resident from eastern Minnesota to southwestern Quebec and southern New Hampshire south to Missouri, Tennessee and northern South Carolina. Dorsal color is cold gray; red morph common (~39% of overall population). The nominate's markings are coarse and sparse and its toes are densely feathered. Its primary song has a terminal tremulous whinny. This is a medium-to-large race, measuring 14 to 18 cm (5.5 to 7.1 in) in wing chord length. The owls of southern Ontario are on the larger end of the scale, of similar size to the relatively big owls of Colorado and Wyoming.
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Megascops asio maxwelliae

(Ridgway, 1877)

Includes Megascops asio swenki. Resident from central Montana, southeastern Saskatchewan, and southern Manitoba south to western Kansas. This race is similar to M. a. asio but dorsal color tends to be a paler gray, the ventrum being whiter and less heavily marked and red morphs tending to paler and rarer (~7% of population). With a wing chord length of 15 to 18 cm (5.9 to 7.1 in), this is the largest race in average linear measurements. This subspecies was named in honor of Martha Maxwell by ornithologist Robert Ridgway of the Smithsonian Institution.
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Megascops asio hasbroucki

(Ridgway, 1914)

Replacement name for the formerly described Megascops asio trichopsis. This subspecies is a resident from Oklahoma panhandle and southern Kansas south to Edwards Plateau of central Texas. This subspecies is also similar to M. a. asio but the dorsal color is buffy gray, the red morph being rare (~5% of population), and markings coarse and dense. This race averages at a similar size as the first two, at 14 to 18 cm (5.5 to 7.1 in) in wing chord length.
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Megascops asio mccallii

(Cassin, 1854)

This includes previously described races like Megascops asio enano and Megascops asio semplei. Resident from southern Texas (Big Bend to lower Rio Grande Valley) and northwestern Chihuahua and northern Coahuila southeast to eastern San Luis Potosí. This race is similar to Megascops asio hasbroucki but its markings are fine and dense so the dorsum looks heavily mottled, with red morph being rare (apparently entirely absent in south Texas). Its body size is smaller to the northern races, with a wing chord length of 13 to 17 cm (5.1 to 6.7 in). Unlike other subspecies, the primary song of Megascops asio mccallii lacks a terminal whinny.
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Megascops asio floridanus

(Ridgway, 1873)

Resident in Florida and southern Georgia west through Gulf Coast states to western Louisiana and north in Mississippi River valley to southeastern Arkansas. This race has a dorsal color that's often rusty-brown (red morph equally common), with fine and dense markings. As described above, this subspecies may come in a true "brown morph". It is the smallest race of eastern screech owl, ranging in wing chord length from 13 to 16 cm (5.1 to 6.3 in).

Habitat

Eastern screech owls inhabit open mixed woodlands, deciduous forests, parklands, wooded suburban areas, riparian woods along streams and wetlands (especially in drier areas), mature orchards, and woodlands near marshes, meadows, and fields. They try to avoid areas known to have regular activity of larger owls, especially great horned owls (Bubo virginianus). Their ability to live in heavily developed areas outranks even the great horned and certainly the barred owl (Strix varia); screech owls also are considerably more successful in the face of urbanization than barn owls (Tyto alba) following the conversion of what was once farmland. Due to the introduction of open woodland and cultivated strips in the Great Plains, the range of eastern screech owls there has expanded. Eastern screech owls have been reported living and nesting in spots such as along the border of a busy highway and on the top of a street light in the middle of a busy town square. They often nest in trees in neighborhoods and urban yards inhabited by humans. In such urban environments, they often meet their dietary needs via introduced species that live close to man such as house sparrows (Passer domesticus), and house mice (Mus musculus). They also consume anole lizards and large insects such as cicadas. They occupy the greatest range of habitats of any owl east of the Rockies. Eastern screech owls roost mainly in natural cavities in large trees, including cavities open to the sky during dry weather. In suburban and rural areas, they may roost in manmade locations such as behind loose boards on buildings, in boxcars, or on water tanks. They will also roost in dense foliage of trees, usually on a branch next to the trunk, or in dense scrubby brush. The distribution of the species is largely concurrent with the distribution of eastern deciduous woodlands, probably discontinuing at the Rocky Mountains in the west and in northern Mexico in the south due to the occupation of similar niches by other screech owls and discontinuing at the start of true boreal forest because of the occupation of a similar niche by other small owls (especially boreal owls (Aegolius funereus). Eastern screech owls may be found from sea level up to 1,400 m (4,600 ft) in elevation in the eastern Rocky Mountains and up to 1,500 m (4,900 ft) in the eastern Sierra Madre Oriental Mountains, although their altitudinal limits in the Appalachian Mountains, near the heart of their distribution, is not currently known.

Behavior

Eastern screech owls are strictly nocturnal, roosting during the day in cavities or next to tree trunks. They are quite common, and can often be found in residential areas. However, due to their small size and camouflage, they are much more frequently heard than actually seen. These owls are frequently heard calling at night, especially during their spring breeding season. Despite their name, this owl doesn't truly screech. The eastern screech owl's call is a tremolo with a descending, whinny-like quality, like that of a miniature horse. They also produce a monotone purring trill lasting 3–5 seconds. Their voice is unmistakable and follows a noticeably different phrasing than that of the western screech owl. The lugubrious nature of the eastern screech owl's call has warranted description such as "A most solemn graveyard ditty, the mutual consolation of suicide lovers remembering the pangs and delights of the supernal love in the infernal groves, Oh-o-o-o, had I never been bor-r-r-n. (James Hubbard Langille, 1884).

Breeding

Their breeding habitat is deciduous or mixed woods in eastern North America. Usually solitary, they nest in a tree cavity, either natural or excavated by a woodpecker. Holes must have a 7 to 20 cm (2.8 to 7.9 in) entrance to accommodate this owl. Usually they fit only in the holes excavated by northern flickers (Colaptes auratus) or pileated woodpeckers (Dryocopus pileatus), as apparently the mid-sized red-bellied woodpecker (Melanerpes carolinensis) make holes that are not large enough to accommodate them. Orchards, which often have trees with crevices and holes as well as meadow voles (Microtus pennsylvanicus), a dietary favorite, are often a preferred nesting habitat. Eastern screech owls will also use nesting boxes erected by humans. Although some people put up nest boxes meant for screech owls, the owls will also take over nest boxes meant for others, such as those for wood ducks (Aix sponsa), house erected for purple martins (Progne subis) and dovecotes put up for rock pigeons (Columba livia), occasionally killing and consuming at least the latter two in the process of taking over the nest box. In a 9-year study comparing the breeding success of eastern screech owls nesting in natural cavities and nesting in nest boxes showed that the fledging rate was essentially the same, although in some years up to 10% more success in the natural cavities. Depending on the origins of the hole being used, eastern screech owl nests have been recorded at anywhere from 1.5 to 25 m (4.9 to 82.0 ft) off the ground. Like all owls, these birds do not actually build a nest; instead, females lay their eggs directly on the bare floor of the nest hole or on the layer of fur and feathers left over from previous meals that lines the bottom of its den. Breeding pairs often return to the same nest year after year.

This species commences egg laying on average about two months after great horned owls but about two weeks before American kestrels (Falco sparveius) and almost throughout the range lays its first egg at some point in April. Eggs are laid at two-day intervals and incubation begins after laying of the first egg. Eggs vary in size in synch with their ultimate body size, ranging from an average of 36.3 mm × 30.2 mm (1.43 in × 1.19 in) in the Northern Rockies to 33.9 mm × 29.2 mm (1.33 in × 1.15 in) in south Texas. From 1 to 6 eggs have been recorded per clutch, with an average of 4.43 in Ohio, 3 in Florida and 4.56 in the north-central United States. The incubation period is about 26 days and the young reach the fledging stage at about 31 days old. Females do most of the incubating and brooding but males will also occasionally take shifts. As is the typical division of labor in owls, the male provides most of the food while the female primarily broods the young, and they will stockpile food during the early stages of nesting, although the male tends to work hard nightly because many nestlings often appear to live almost entirely off of freshly caught insects and invertebrates. The male's smaller size make it a superior in its nimbleness, which allows it to catch insects and other swift prey. Eastern screech owls are single brooded, but may re-nest if the first clutch is lost especially towards the southern end of its range. When the young are small, the female tears the food apart for them. The female, with her larger size and harder strike, takes on the duty of defending the nest from potential threats and even humans may be aggressively attacked, sometimes resulting in them drawing blood from the head and shoulders of human passers-by.

Feeding Habits

Mortality

Parasites

This species has the potential to be infected by several parasites including Plasmodium elongatum, Plasmodium forresteri and Plasmodium gundersi.

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