Eastern screech owl
The eastern screech owl or eastern screech-owl is a small 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 in length and weigh. Among the differently sized races, length can average from. The wingspan can range from. In Ohio, male owls average and females while in central Texas, they average and, respectively. They have either rusty or dark gray intricately patterned plumage with streaking on the underparts. Midsized by screech-owl standards, these birds are stocky, short-tailed and broad-winged 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 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 are actually some of the heaviest screech owls, the largest tropical screech owls do not exceed them in average or maximal weight, but they are surpassed in length by Balsas, long-tufted, white-throated, and rufescent owls, in roughly increasing 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 morphs is known from Tennessee and Illinois. A rarer "brown morph" is known, recorded exclusively in the south, which may be the occasional product of hybridation between the morphs. In 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 also exists in western Canada and the north-central United States.
Confusion with other species
In the closely related western screech owl, no color morphs are known; 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 feature is the bill color, which is considerably darker in the western and olive-yellow in the eastern; their voices also differ. 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, whiskered screech owl, and the flammulated owl, are distinguished by their increasingly smaller body and foot size, different streaking pattern on breast, 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 differently colored and the only other small owl, the northern saw-whet owl 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.- M. a. asio includes previously described races no longer considered valid such as M. a. carolinensis, M. a. naevius and M. a. striatus. It is resident from eastern Minnesota to southwestern Quebec and southern New Hampshire south to Missouri, Tennessee, and northern South Carolina. Dorsal color is cold gray; the red morph is common. 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 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.
- M. a. maxwelliae. Includes M. a. 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. With a wing chord length of, 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.
- M. a. hasbroucki. Replacement name for the formerly described M. a. 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, and markings coarse and dense. This race averages at a similar size as the first two, at in wing chord length.
- M. a. mccallii includes previously described races such as M. a. enano and M. a. semplei. Resident from southern Texas and northwestern Chihuahua and northern Coahuila southeast to eastern San Luis Potosí, this race is similar to M. a. hasbroucki, but its markings are fine and dense so the dorsum looks heavily mottled, with red morphs being rare. Its body size is smaller to the northern races, with a wing chord length of. Unlike other subspecies, the primary song of M. a. mccallii lacks a terminal whinny.
- M. a. floridanus is resident in Florida and southern Georgia west through Gulf Coast states to western Louisiana and north in the Mississippi River valley to southeastern Arkansas. This race's dorsal color is often rusty-brown, with fine and dense markings. As described above, this subspecies may occur in a true "brown morph". It is the smallest race of eastern screech owl, ranging in wing chord length from.
Habitat
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 does not 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 voices are unmistakable and follow 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-o that I never had been bor-r-r-r-n!.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 entrance to accommodate this owl. Usually, they fit only in the holes excavated by northern flickers or pileated woodpeckers, as apparently the midsized red-bellied woodpecker make holes that are not large enough to accommodate them. Orchards, which often have trees with crevices and holes, as well as meadow voles, a dietary favorite, are often preferred nesting habitats. Eastern screech owls also use nesting boxes erected by humans. Although some people put up nest boxes meant for screech owls, the owls also take over nest boxes meant for others, such as those for wood ducks, houses erected for purple martins, and dovecotes put up for rock pigeons, occasionally killing and consuming at least the latter two in the process of taking over the nest box. 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 occurred in the natural cavities. Depending on the origins of the hole being used, eastern screech owl nests have been recorded from 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 line 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 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 in the Northern Rockies to in south Texas. From one to six eggs have been recorded per clutch, with an average of 4.4 in Ohio, 3.0 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 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 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 on freshly caught insects and invertebrates. The male's smaller size make it superior in its nimbleness, which allows it to catch insects and other swift prey. Eastern screech owls are single-brooded, but may renest 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
Like most predators, eastern screech owls are opportunistic hunters. Due to the ferocity and versatility of their hunting style, early authors nicknamed eastern screech owls "feathered wildcats". In terms of ecological niche, they have no easy ecological equivalent in Europe, perhaps the closest being the little owl, the similar looking Eurasian scops owl being smaller and weaker and the long-eared owl more fully dependent on rodents. The success of eastern screech owls in North America may be the reason long-eared owls are much more restricted to limited northern forest habitat in North America than they are in Europe. Eastern screech owls hunt from dusk to dawn, with most hunting being done during the first four hours of darkness. A combination of sharp hearing and vision is used for prey location. These owls hunt mainly from perches, dropping down onto prey. Occasionally, they also hunt by scanning through the treetops in brief flights or hover to catch prey. This owl mainly hunts in open woodlands, along the edges of open fields or wetlands, or makes short forays into open fields. When prey is spotted, the owl dives quickly and seizes it in its talons. Small prey usually is swallowed whole on the spot, while larger prey is carried in the bill to a perch and then torn into pieces. An eastern screech owl tends to frequent areas in its home range where it hunted successfully on previous nights. The eastern screech owl's sense of hearing is so acute, it can even locate mammals under heavy vegetation or snow. The bird's ears are placed asymmetrically on its head, enabling it to use the differences between each ear's perception of sound to home in on prey. Additionally, the feathers the eastern screech owl uses to fly are serrated at their tips. This muffles the noise the bird makes when it flaps its wings, enabling it to sneak up on prey quietly. Both the specialized ear placement and wing feathers are a feature shared by most living owl species to aid them in hunting in darkness.During the breeding season, large insects are favored in their diet, with invertebrates often comprising more than half of the owls' diet. Some regularly eaten insects include beetles, moths, crickets, grasshoppers, and cicadas, although they likely consume any commonly available flying insect. Also taken are crayfish, snails, spiders, earthworms, scorpions, leeches, millipedes, and centipedes. Small mammals, ranging in size from shrews to young rabbits, are regular prey and almost always become the owl's primary food during winter. Small rodents such as microtine rodents and mice comprise about 67% of mammals taken, although rodents of a similar weight to the owl, such as rats and squirrels are also taken. Jumping mice, chipmunks, moles, and bats may be taken occasionally. Small birds such as chickadees, swallows, sparrows, and warblers are the most common avian prey, and such species are normally caught directly from their nocturnal perches or during nocturnal migration. In Ohio, the most commonly reported avian prey species, and most commonly stored food items behind meadow voles, were yellow-rumped warblers and white-throated sparrows. Abundant midsized avian or largish passerine prey are also not uncommon foods, such as mourning doves, downy woodpeckers, northern flickers, blue jays, American robins, European starling, red-winged blackbirds, and common grackles. However, larger avian prey are sometimes caught, including northern bobwhite and American woodcocks and even rock pigeons and ruffed grouse, most likely young or fledgling aged birds, but all of which are likely to be heavier than the screech owls themselves. All told, more than 100 species of bird have been hunted by eastern screech owls. Irregularly, small fish, small snakes, lizards, baby soft-shelled turtles, small frogs, toads, newts, and salamanders are also preyed upon. They have even been observed hunting for fish at fishing holes made by people or cracks in ice at bodies of water during winter. The most commonly reported fish prey in Ohio were American gizzard shad and green sunfish. Brown bullheads have been captured by eastern screech owls along coastal areas during winter.
From hundreds of prey remains from Ohio, 41% were found to be mammals, 18% were birds, and 41% were insects and other assorted invertebrates. Of vertebrates taken in the nesting season, 65% were birds, 30% were mammals, 3% were fish, and less than 2% were reptiles and amphibians. In Michigan, among winter foods, 45-50% were meadow voles, 45% were white-footed mice and 1-10% were birds; during the summer, these respective numbers changed to 30, 23, and 19%, with as much as 28% of the food in summer being crayfish. Due to meeting the needs of their nestlings, eastern screech owls frequently consume less per day during summer than they do during winter. Five owls captured in April, averaging about in males and in females, gained on average when captured in fall and when captured in winter. In Michigan, screech owls consumed about 25% of their own weight per day during winter against 16% of their weight in summer. The average weight of vertebrate prey for screech owls in Michigan is In Wisconsin, the average weight of vertebrate prey is. While much of their insect prey can weigh only a fraction of a gram, their largest prey, such as adult rats and pigeons and juvenile rabbits and gamebirds, can weigh up to at least.