The barred owl (Strix varia), also known as the northern barred owl, striped owl, or more informally, hoot owl or eight hooter, is a North American large species of owl. A member of the true owl family, Strigidae, they belong to the genus Strix, which is also the origin of the family's name under Linnaean taxonomy. Barred owls are largely native to eastern North America, but have expanded their range to the West Coast of North America, where they are considered invasive.Evers, L. (2014). Beyond anyone's control. Northwest Science, 88(1), 65–67.Kelly, E. G. (2001). The range expansion of the northern barred owl: an evaluation of the impact on spotted owls. Thesis, Oregon State University. Mature forests are their preferred habitat, but they can also acclimate to various gradients of open woodlands.Mazur, K. M. & James, P.C. (2020). "Barred Owl (Strix varia)", version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. Their diet consists mainly of small mammals, but this species is an opportunistic predator and is known to prey upon other small vertebrates such as birds, reptiles, and amphibians, as well as a variety of invertebrates.
Barred owls are brown to gray overall, with dark striping on the underside. They have typical nesting habits for a true owl, tending to raise a relatively small brood often in a tree hollow or snag (but sometimes also in other nesting sites) in forested areas. As a result of the barred owl's westward expansion, the species has begun to encroach on the range of the related and threatened spotted owl (S. occidentalis). Evidence shows the assorted threats posed by the invading barred species are only increasing. In response, biologists have recommended culling operations to mitigate their negative effect on the spotted owl species.
Basics
The barred owl was first described by Philadelphia naturalist Benjamin Smith Barton in 1799. The species was named due to the varied directions the dusky markings take on their undersides.Barton, B. S. (1883). Barton's Fragments of the Natural History of Pennsylvania. Willughby Society.
The barred owl is roughly intermediate in size between the larger Ural and the smaller tawny owl, but the structural features of its relatively short and decurved claws more so resemble the tawny species, as does its dietary and habitat ecology. The spotted owl has been hypothesized to be within a superspecies with the barred owl.Mayr, E., & Short, L. L. (1970). Species taxa of North American birds: a contribution to comparative systematics. Nuttall Ornithological Club. However, genetic testing reveals very early divergence (likely at or near their ancestor's entry to North America) between spotted and barred owls. A fossil species once called Strix brea from the early Pleistocene in California does little to resolve the ancestry of modern species, given its ambiguous relationship to any living Strix species. The fossil species was larger (more similar in size and slenderness to the spotted owl, albeit with a slightly smaller skull and geographically isolated from that species) and longer-legged than either the spotted or barred owls and is now considered to be in a separate genus, Oraristrix. Pleistocene era fossils of probable barred owls are known from Florida, Tennessee and Ontario.
Subspecies
The subspecies of the barred owl vary mostly by region, with slight to moderate variation by coloring, size, and extent of feathering on the toes. Although several have been described in the past, the barred owl may include only three subspecies, subsequent to the separation of the fulvous and cinereous forms.Peters, J. L. (1940). Check-list of birds of the world. Vol. 4. Cambridge: Harvard Univ. Press.
S. v. varia (Barton, 1799): The northern barred owl lives throughout the Northeastern United States and the Upper Midwest, ranging as far south as Oklahoma, the Carolinas, and northern Georgia. It is also considered to comprise all western "invader" birds found as far west as California and British Columbia. Genetic study of westerly birds shows a substantial isolation, though, possibly up to the subspecific level, of the western and eastern populations of the northern owls, with an estimated divergence around 7,000 years ago, perhaps indicating an unknown history of the species in remote forests of northern and central Canada (farther west of what was considered their original distribution) that radiated more recently to comprise the western populations. This race is generally the typical mid gray-brown variety of barred owl. However, a paler variation with very washed out markings and a more pure whitish base color is known (in eastern Canada such as Quebec), formerly considered a race S. v. albescens, as well as darker and browner variation in northern Minnesota (formerly S. v. brunnescens). This subspecies is fairly large (described as the largest on average with the probable separation of the cinereous owl). The wing chord and tail length may measure from and in males and and in females, respectively. One nominate bird had a tarsal length of and the culmen from the cere may measure . S. v. georgica (Latham, 1801): The southern barred owl, or Florida barred owl, is found in southern North Carolina closer to the coast along to broadly through Georgia and all of Florida. This is the smallest of the three subspecies on average. Known wing chord lengths can vary from . Tail length is and the bill from the cere is . Males in Florida were found to weigh from , with averages in two samples of , while two females weighed , respectively. It therefore appears to show less pronounced sexual dimorphism than the northern barred owl race. S. v. helveola (Bangs, 1899): The Texas barred owl comprises most barred owls found in Texas. Its distributional range is considered to range as far north as Lee County, east to Chambers County, west to Kerr County, and south to Nueces County.Howell, S. N., & Webb, S. (1995). A guide to the birds of Mexico and northern Central America. Oxford University Press.Oberholser, H. C. (1974). The Bird Life of Texas. University of Texas Press, Austin, TX, USA. In this race, the ground coloration tends to pale gingery-cream and the back and head tend to be a pale brown ranging into an almost cinnamon color. The toes can vary from rather bare to slightly bristled. This race is similar to other barred owls in size, perhaps averaging marginally smaller than those in the nominate race, but its bill and feet are larger on average than the other two races.
Description
The barred owl is considered somewhat subdued and drab in coloration compared to the sometimes rich coloring of other sympatric owls.Hume, R. (1991). Owls of the world. Running Press, Philadelphia. Overall, this owl is greyish-brown or brown, which extends from the head to the back. Barred owls are scalloped with white bars on the mantle and the back, also bearing some whitish spotting on the wing coverts. The underside has a pale, creamy gray-brown base color (ranging into dirty white in the palest individuals) overlaid about the throat and upper chest with horizontal, slightly crescent-shaped barring (hence its common name), while the belly is boldly streaked in a vertical pattern. The streaking is usually blackish, dusky brown, or sometimes reddish-brown. The head is fairly large (although not especially so for a species in Strix) and rounded with no ear tufts.Owls of the World: A Photographic Guide by Mikkola, H. Firefly Books (2012), Holt, D.W., Berkley, R., Deppe, C., E. Rocha, P., Petersen, J.L., Rangel Salazar, J.L., Segars, K.P., Wood, K.L. & Marks, J.S. (2019). "Typical Owls". In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. The facial disc is pale grayish-brown with darker yet subtle concentric lines. The bill is pale straw-yellow (occasionally showing a mild greenish tint), while the cere (a bare structure at the base of the beak) is "horn-colored". Its eyes are a dark brown color; the eyes may appear intensely black in the field, and although large, are fairly closely set.
The barred owl has well-developed eye anatomy. As is typical of owls, its ocular anatomy is quite distinct from diurnal raptors, especially in terms of the photoreceptor cells, as the species has a very large number of rod cells in the quite sensitive retina. However, the pecten oculi is smaller relative to the size of the large ocular globe (other large owls are known to have similar pecten proportions). The vision in limited or almost no light during a laboratory study of a barred owl was found to be similar to that of other owls, including the long-eared owl (Asio otus) and American barn owl (Tyto furcata). The tarsi and toes are feathered up to the dark gray, black-tipped talons. These feathers are sparser and more bristled in the southern races. On individuals with bare sections of their toes, the toes are yellowish gray in color. The flight feathers are barred with whitish buff and brown, while the tail is brown or grayish-brown with four or five whitish bars. A young barred owl with its second set of down feathers is fluffy brownish-white, with indistinct darker barring on its head, back, and mantle, but quickly becomes a juvenile, which resembles adults but has less distinct markings (especially about the head and neck), more buff coloring overall, often some remnant down, pinkish skin, and a pale, blue-green cere. Also, the tail at this age may have as many as seven bands (though sometimes has four, like adults). Full adult plumage is obtained via molt after about a year as well as adult bare part characteristics. A study of tail molt in Washington showed that it tends to occur relatively quickly, and that young individuals are difficult to age by state of molt alone. Southern barred owls tend to be darker and slightly smaller than northerly ones.Karalus, K. E. & Eckert, E.W. (1974). The owls of North America (north of Mexico). Garden City, NY: Doubleday and Co. Rare captive and wild barred owls with albinism have been described and are pure white, but tend to retain their brown eyes.
The barred owl is a large species. The adult measures from in length, while the wingspan may range from .Barred Owl (Strix varia) – Information, Pictures, Sounds. The Owl Pages (2015-11-04). Retrieved on 2016-08-01.Ridgway, R., & Friedmann, H. (1914). The Birds of North and Middle America: A Descriptive Catalog of the Higher Groups, Genera, Species, and Subspecies of Birds Known to Occur in North America, from the Arctic Lands to the Isthmus of Panama, the West Indies and Other Islands of the Caribbean Sea, and the Galapagos Archipelago (Vol. 50). US Government Printing Office. The wing area (measured by area relative to the body mass) is quite intermediate among American owls, with the wing loading being lower than larger, but proportionately small-winged larger owls and even than some smaller owls. The barred has high wing loading, which is related to hunting technique, with higher wing-loaded owls typically hunting from a perch, with only a brief flight necessary to obtain food, while lower wing-loaded owls often hunt their prey from active flight. As is the case in most owls, the various wing feathers of barred owls are uncharacteristically soft and bear a comb-like shape, which in turn renders their flight functionally silent during their hunts. Like most birds of prey, the female is larger than the male barred owl, sometimes described as reverse sexual dimorphism (because males are typically larger than females in most nonraptorial birds).