Eastern screech owl

The eastern screech owl was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae. He placed it with all the other owls in the genus Strix and coined the binomial name Strix asio. Linnaeus based his account on the "little owl" that had been described and illustrated by the English naturalist Mark Catesby in his book The Natural History of Carolina, Florida and the Bahama Islands. The specific epithet is the Latin word for a type of eared owl. The eastern screech owl is now one of 22 screech owls placed in the genus Megascops that was introduced in 1848 by the German naturalist Johann Kaup. Five subspecies are typically recognised 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 (Linnaeus, 1758) 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 (about 39% of overall population). • M. a. hasbroucki (Ridgway, 1914). 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 (~5% of population), and markings coarse and dense. This race averages at a similar size as the first two, at in wing chord length. • M. a. mccallii (Cassin, 1854) includes previously described races such as M. a. enano and M. a. 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 M. a. hasbroucki, but its markings are fine and dense so the dorsum looks heavily mottled, with red morphs being rare (apparently entirely absent in South Texas). 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 (Ridgway, 1873) 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 (red morph equally common), 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 . ==Description==

Adults range from in length and weigh . 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 (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 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. Evidence of higher metabolic rates was shown by a higher proportion of gray morphs in the rural areas surrounding Waco, TX compared to the warmer suburban areas. Rufous screech owls also had higher mortality during cold winters. ==Distribution and 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 American barn owls (Tyto furcata) 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 humans 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 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 in elevation in the eastern Rocky Mountains and up to 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 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 (Colaptes auratus) or pileated woodpeckers (Dryocopus pileatus), as apparently the midsized red-bellied woodpecker (Melanerpes carolinensis) make holes that are not large enough to accommodate them. In terms of ecological niche, they have no easy ecological equivalent in Europe, perhaps the closest being the little owl (Athene noctua), the similar looking Eurasian scops owl (Otus scops) being smaller and weaker and the long-eared owl (Asio otus) more fully dependent on rodents. The success of eastern screech (and western 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. 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 (Sylvilagus ssp.), are regular prey and almost always become the owl's primary food during winter. Small rodents such as microtine rodents and mice account for about 67% of mammals taken, although rodents of a similar weight to the owl, such as rats and squirrels, especially the red squirrel (Tamiasciurus hudsonicus), are also taken. Jumping mice (Zapus ssp.), chipmunks, moles, and bats (especially the little brown bat (Myotis lucifugus) may be taken occasionally. Small birds such as chickadees (Poecile ssp.), swallows, sparrows, finches, flycatchers, 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 (Setophaga coronata) and white-throated sparrows (Zonotrichus albicollis). Climate, food sources, and predator presence are some potential factors that impact the behaviors of suburban and rural eastern screech owls. Living in suburbia can have some additional impacts on eastern screech owl behavior such as secondary poisoning, vehicles, and more predation and competition from raccoon, opossum and squirrels. found that there were larger average brood sizes and earlier average fledging dates of eastern screech owls shown in moderate and high-density suburban areas than in low-density suburban and rural areas. There are various differences in habitat that have impacts on the nesting behaviors of eastern screech owls. Eastern screech owl feeding behaviors have also been shown through previous research to be impacted by whether the owl lived in a rural or suburban area. In a previous study, prey diversity for eastern screech owls peaked in low-density suburban areas. A previous study showed that as suburban climates got warmer over the course of a few years, eastern screech owls started nesting an average of 4.5 days earlier annually. There were also more avian prey and a 93% success rate in annual nests. Bird baths and feeders located in the suburban habitats were also noted as being likely factors in enhancing residence successes. ==Mortality==

While eastern screech owls have lived for over 20 years in captivity, wild birds seldom, if ever, live that long. Mortality rates of young and nestling owls may be as high as 70% (usually significantly less in adult screech owls). Many losses are due to predation. Common predators at screech owl nests including Virginia opossums (Didelphis virginiana), American minks (Neogale vison), weasels (Mustela and Neogale sp.), raccoons (Procyon lotor), ringtails (Bassariscus astutus), skunks (Mephitis and Spilogale sp.), snakes, crows (Corvus sp.), and blue jays (Cyanocitta cristata). Eastern fox squirrels (Sciurus niger) may raid the tree holes being used by eastern screech owls, not only destroying or consuming the eggs, but also displacing the adult owls from the hole to use the hole for themselves. Adults have fewer predators, but larger species of owls do take them, since they have similar periods of activity. Larger owls known to have preyed on eastern screech owls have included great horned owls (Bubo virginianus), barred owls (Strix varia), spotted owls (Strix occidentalis), long-eared owls (Asio otus), short-eared owls (Asio flammeus), and snowy owls (Bubo scandianus). Diurnal birds of prey may also kill and eat them, including Cooper's hawks (Accipiter cooperii), northern harriers (Circus cyaenus), red-tailed hawks (Buteo jamaicensis), red-shouldered hawk (Buteo lineatus) and rough-legged hawks (Buteo lagopus). Most prolific by far of the eastern screech owl's avian predators is the great horned owl, which can destroy up to 78% of a local population, but locally, Cooper's hawks and barred owls are almost as serious of a threat. A most dramatic case illustrating the owl food chain involved a barred owl, which upon examination after being shot in New England, contained a long-eared owl in its stomach that, in its own stomach, contained an eastern screech owl. All other common owls in this species range also live on similar rodent prey, but direct competition is obviously disadvantageous to the screech owl. One exception is the even smaller northern saw-whet owl, on which eastern screech owls have been known to prey. In rural Michigan, 9 different species of owls and diurnal raptors including the screech owl fed primarily on the same four species of small rodents from the Peromyscus and Microtus genera. Eastern screech owls have had nesting attempts fail due to biocide poisoning, which causes the thinning of eggs and failure of nests, but seemingly not to the overall detriment of the species. Collisions with cars, trains, and windowpanes kill many screech owls, the earlier especially while feeding on road-side rodents and road kills. Parasites This species has the potential to be infected by several parasites, including Plasmodium elongatum, Plasmodium forresteri, and Plasmodium gundersi. ==Image gallery==

EasternScreechOwl23.jpg|Gray morph screechowl23.jpg|Gray morph EasternScreechOwlBillWaller.jpg|Red morph Eastern Screech-Owl (Megascops asio) RWD.jpg|Red morph Eastern Screech Owl RWD1 at CRC.jpg|Red morph and gray morph at a raptor center Eastern Screech Owl-red-phase2.jpg|Red morph Eastern screech owl rehabilitated after eye injury (44333).jpg|Rescued after an eye injury Bird taxidermy at Nairobi National Museum (10).jpg|taxidermy at Nairobi National Museum ==References==