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Morphology

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medium-sized, brown owl. round or oval irregular white spots on head, neck, back, and underparts. no ear tufts. flight feathers dark brown barred with light brown or white. female larger than male.

Other Physical Features: endothermic ; bilateral symmetry

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Emiley, A. 1999. "Strix occidentalis caurina" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_occidentalis_caurina.html
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Ann Emiley, University of Michigan-Ann Arbor
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Habitat

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Northern Spotted Owls inhabit old growth forests and younger forests with remnants of larger trees. They prefer these forests because they provide a canopy forprotection from predators and the elements, large open spaces for flight, wood debris for nests, and old hollow trees for nesting sites.

Terrestrial Biomes: forest

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Emiley, A. 1999. "Strix occidentalis caurina" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_occidentalis_caurina.html
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Ann Emiley, University of Michigan-Ann Arbor
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Distribution

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Old growth forests in British Columbia, Washington, Oregon, and northern California

Biogeographic Regions: nearctic (Native )

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Emiley, A. 1999. "Strix occidentalis caurina" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_occidentalis_caurina.html
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Ann Emiley, University of Michigan-Ann Arbor
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Untitled

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The Northern Spotted Owls are thought to live as long as ten years in the wild and up to 15-20 years in captivity.

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Emiley, A. 1999. "Strix occidentalis caurina" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_occidentalis_caurina.html
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Ann Emiley, University of Michigan-Ann Arbor
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Behavior

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Perception Channels: visual ; tactile ; acoustic ; chemical

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Emiley, A. 1999. "Strix occidentalis caurina" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_occidentalis_caurina.html
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Ann Emiley, University of Michigan-Ann Arbor
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Conservation Status

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Harvesting of old growth forests affects the owls by decreasing the area of appropriate habitat. Somewhere between 54% and 99% of appropriate habitat has been lost. Forests can be reinhabited 40-100 years after logging if snags, coarse debris, and some trees with cavities are left by loggers. Recently, the survival rate of the juveniles has also been a problem. Protecting old growth forests would protect these owls, but the human costs are high. Northern Spotted Owls have been studied extensively, and they are the subject of much current debate and litigation.

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Emiley, A. 1999. "Strix occidentalis caurina" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_occidentalis_caurina.html
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Ann Emiley, University of Michigan-Ann Arbor
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Benefits

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Since the owls became threatened in 1990, logging in old growth forests has been restricted, resulting in job loss and economic disruption in the Pacific northwest. This has become a very important political and economic issue.

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Emiley, A. 1999. "Strix occidentalis caurina" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_occidentalis_caurina.html
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Ann Emiley, University of Michigan-Ann Arbor
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Benefits

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These birds play an important role in the food chain of old growth forests. The owls depend on a healthy diverse ecosystem for survival. They help keep the populations of their prey under control. They are also an attraction to birdwatchers, who bring in tourist dollars.

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Emiley, A. 1999. "Strix occidentalis caurina" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_occidentalis_caurina.html
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Ann Emiley, University of Michigan-Ann Arbor
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Trophic Strategy

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Northern Spotted Owls are nocturnal birds that feed primarily on small mammals, but also take birds, reptiles and insects. Northern flying squirrels are their main prey, but they also consume significant numbers of red tree voles, deer mice, and woodrats.

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Emiley, A. 1999. "Strix occidentalis caurina" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_occidentalis_caurina.html
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Ann Emiley, University of Michigan-Ann Arbor
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Reproduction

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Northern Spotted Owls mate in pairs, usually for life. They nest in hollow trees or crevices in cliffs; spots that are well hidden and that provide protection from extreme temperatures. They sometimes use squirrel or raptor nests as platforms on which to build their own nests. Pairs form in February or March and egg laying takes place in March and April. They most commonly lay two to three white eggs. One brood is produced each season. Eggs are incubated for 30 days, and the young fledge 34-36 days after hatching. The female incubates the egg and broods the young for the first 8-10 days after hatching; during this period, the male brings her food. Some owls forage during the day to take care of the young at night.

Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous

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Emiley, A. 1999. "Strix occidentalis caurina" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_occidentalis_caurina.html
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Ann Emiley, University of Michigan-Ann Arbor
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Behavior

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Behavior

The northern spotted owl uses its agility and excellent flying skills to travel the forest canopy, and when hunting its prey on the forest floor will use gliding flight to slow its speed and hover over its victim. A series of short climbing flights from branch to branch, rather than one continuous flight, is used when the bird wants to gain altitude. Northern spotted owls are solitary and very territorial birds and they continuously survey their arboreal neighborhoods to ensure that no intruders are disturbing their habitat. Territorial disputes among neighboring owls are rare, and to ensure limited territorial conflicts, the spotted owl announces its presence to nearby residents with a distinct call. Individuals are not particularly aggressive in spurning intruders of the opposite sex, and will, in fact, occasionally roost with members of the opposite sex other than their original mate.Roosting and interacting typically take place approximately 4–6 weeks before egg laying. Copulation begins 2–3 weeks before nesting and occurs frequently prior to egg laying. A pair of spotted owls requires a large amount of land, ideally old-growth forests, for hunting and nesting. When they are required to defend their nest from its usual predators such as common ravens (Corvus corax), northern goshawks (Accipiter gentilis), and Cooper’s hawks (Accipiter cooperii), intruders will either be chased or attacked with talons, after being warned by a series of agitated vocalizations.

Reference

Gutierrez, Ralph, and Andrew Carey. 1985. Ecology and management of the Spotted Owl in the Pacific Northwest. Portland: U.S. Department of Agriculture, Forest Service—Pacific Northwest Forest and Range Experiment Station.

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Authors: Delsey Huitt, Sam McGough, Nico McGuire, Matinn Miller.Editor: Gordon Miller, Seattle University EVST 2100
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Conservation Status

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Beginning in the 1990s, the conservation status of the northern spotted owl has been the focus of contentious political debate, significant economic concern, and intense scientific research. Habitat degradation and fragmentation resulting from clear cutting and selective logging of commercially valuable old-growth forests pose the major threat. But competition from barred owls, as well as the impact of diseases such as West Nile Virus and avian malaria, also present challenges to survival. Climate change will likely also play a role and the National Audubon Society projects that 98% of the spotted owl’s winter range could disappear by 2080. In 2011 the annual population decline of Strix occidentalis caurina was estimated a 3% across its range as a whole and 7% in Washington State. It is currently listed as “Threatened” by the U.S. Fish and Wildlife Service and as “Endangered” by the Washington State Department of Fish and Wildlife. With more than half of the former old-growth habitat now gone, several management plans, most notably the controversial Northwest Forest Plan, as well as captive breeding programs, have been developed. But continued monitoring and perhaps habitat preservation or restoration will be needed to ensure healthy populations of this species into the future.

References

  • Seattle Audubon. 2016. "Spotted Owl." Seattle Audubon Society, BirdWeb. http://www.birdweb.org/Birdweb/bird/spotted_owl. Accessed June 2, 2016.
  • Audubon. 2016. “Spotted Owl.” National Audubon Society, The Climate Report. http://climate.audubon.org/birds/spoowl/spotted-owl. Accessed June 16, 2016.
  • BirdLife International. 2015. Strix occidentalis. The IUCN Red List of Threatened Species 2015: e.T22689089A85096847. http://www.iucnredlist.org/details/22689089/0. Accessed June 16, 2016.

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General Ecology

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General Ecology

The biggest threat to the northern spotted owl is the loss of its preferred old-growth habitat as a result of logging and deforestation. This threat is exacerbated by natural disasters such as fires and windstorms. The increasing number of barred owls who have greatly expanded from the eastern United States to western Canada, the Pacific Northwest, and northern California has had an adverse effect on spotted owls. Barred owls, in contrast to their spotted cousins, tend to benefit from anthropogenic alterations to forests and thus are often able to displace native spotted owls, sometimes also breeding with them and creating a species of hybrids. Climate change, although maybe considered a marginal threat to spotted owls, is projected to bring wetter winters and drier summers to the habitats of the northern spotted owl. Long summer droughts could increase the limited rates of insect exposure, reducing food in the area. Summer droughts also introduce more forest fires in the old-growth forest areas that the owls depend on.

References

  • Davis, Raymond J., Katie M. Dugger, Shawne Mohoric, Louisa Evers, and William C. Aney. 2011. Northwest Forest Plan - The First 15 years (1994-2008): Status and Trends of Northern Spotted Owl Populations and Habitats. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.
  • Gutiérrez, Ralph, and Andrew Carey. 1985. Ecology and management of the Spotted Owl in the Pacific Northwest. Portland: U.S. Department of Agriculture, Forest Service—Pacific Northwest Forest and Range Experiment Station.

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Habitat

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Northern spotted owls reside in British Columbia, Washington State, Oregon, northern California and British Columbia. Their highest population densities are in southern Oregon and northern California because of the abundance of prey. Although these owls have been found to roost in a wide variety of habitats, at elevations from sea level to 1200m, they prefer dense canopy enclosures that are comprised of mature, wide-branched, old-growth trees, in stands with both snags and live trees with broken tops. Typical trees in these supportive habitats include Douglas fir, cedar, spruce, and hemlock, which ideally provide space among the branches in the lower part of the canopy to allow for flight between trees. These specific habitats are typically found only in forests that are at least 150-200 years old. Research has shown that both foraging and nesting owls have nearly identical habitat preferences. Within these canopies, the northern spotted owls search for cool microclimates that are typically in the lower third of the forest near streambeds. During the summer months, they will change locations depending on the climate within the canopy. Because of their sensitivity to varying temperatures, it has been hypothesized that northern spotted owls also reside within old growth canopies to avoid heat stress.




Reference

Washington Forest Protection Association. 2016. “Northern Spotted Owl Conservation in Washington State.” http://www.northernspottedowl.org/index.html. Accessed June 2, 2016.

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Life Cycle

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Northern spotted owls typically live up to 10-15 years, with even longer life spans recorded in captivity. Their mating season usually starts in February or March, and may vary slightly depending on the geographic location and elevation. Throughout their life cycle, these owls are generally monogamous, and usually do not search for another partner if their original one were to die prematurely. Nests are typically sought out by the male owl before the mating season and are built in snags. They seek out such trees to find cavities or depressions in the trunks, which the female burrows into to enhance the shape for a more apt nest. The owls will utilize feathers, natural sources such as branches, and unnatural sources such as cans and wires to construct their nests, which usually measure 42-59 cm in diameter. They have also been found to reuse nesting sites, as well as actual nests, from previous seasons.

Reference

National Wildlife Federation. 2016. “Northern Spotted Owl.” https://www.nwf.org/Wildlife/Wildlife-Library/Birds/Northern-Spotted-Owl.aspx. Accessed June 2, 2016.

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Overview

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The northern spotted owl (Strix occidentalis caurina), due to its central role in the so-called “timber wars” of the Pacific Northwest in the 1980s and ‘90s, is one of the most scientifically studied and publically debated birds in the world. It belongs to the Strigidae family, which is the larger of the two families of owls. They average around 18 inches in length, with an average wingspan of 48 inches, and weigh an average of 1 to 2 pounds, the males being slightly smaller than the females. They are mostly brown and have oval and circular white spots randomly dispersed on the head, back, neck, and underparts. Their native region spans the north Pacific Coast of the United States, beginning in southwest British Columbia, extending through Washington and Oregon, and ending in northern California. Two other subspecies, the California spotted owl (Strix occidentalis occidentalis) and the Mexican spotted owl (Strix occidentalis lucida), inhabit central and southern California and the U.S. Southwest and central Mexico respectively. The northern spotted owl is found particularly in old growth forests with high and open canopies that allow them to fly in and around the trees and branches. More specifically, they can be found in areas with a high concentration of trees with broken tops, deformed branches, or natural tree hollows that offer good nesting sites. The owls mate (usually for life) in February and March, and once the new clutch of eggs has hatched the mother protects and attends to the hatchlings for 8-10 days while the father hunts and brings food for the offspring. In just over a month, the offspring fledge. Northern spotted owls reach sexual maturity in about a year, but will often wait until they are 2 to 5 years old to begin mating. As are most owls, S. occidentalis is a nocturnal bird that preys mostly on small mammals, but it will not shy away from other meals such as birds, reptiles, and certain insects. The owl’s most frequent meal is the also nocturnal northern flying squirrel, supplemented by red tree voles, deer mice, and woodrats. The northern spotted owl relies on its agility and maneuverability in order to navigate the canopy and while hunting adjusts its flight speed to enable it to hover over its prey and organize its attack. A pair of owls requires a large area of forest in order to nest and hunt and often claim upwards of 35 square kilometers as their own. The birds are extremely territorial, constantly surveying their domain to keep any other owls or any unwanted visitors from disturbing their habitat. Like many birds, each owl has a distinct call, which is used to determine which land is occupied and which is vacant.

References

  • All About Birds. 2016. “Spotted Owl.” Cornell university, Cornell lab of Ornithology. https://www.allaboutbirds.org/guide/Spotted_Owl/id. Accessed June 1, 2016.
  • Emiley, A. 1999. “Strix occidentalis caurina.” Animal Diversity Web. Ann Arbor, Michigan. http://animaldiversity.org/accounts/Strix_occidentalis_caurina/. Accessed June 2, 2016.
  • Gutiérrez, R.J., A.B. Franklin, and W.S. Lahaye. 1995. “Northern Spotted Owl.” The Birds of North America (P.G. Rodewald, ed.) Ithaca: Cornell Lab of Ornithology. https://birdsna.org/Species-Account/bna/species/spoowl/introduction. Accessed June 3, 2016.
  • Lebbin, Daniel J., Michael J. Parr, and George H. Fenwick. 2010. The American Bird Conservancy Guide to Bird Conservation. Chicago: University of Chicago Press.
  • Seattle Audubon. 2016. "Spotted Owl." Seattle Audubon Society, BirdWeb. http://www.birdweb.org/Birdweb/bird/spotted_owl. Accessed June 2, 2016.

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Reproduction

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Females will lay a clutch of approximately one to four pure white eggs each season. Each gestation period is roughly 30 days, after which the mother owl will sit with the hatchlings for 8-10 days. The male owls typically perform most of the foraging and will bring back sustenance for the female and owlets. Northern spotted owlets fledge about 34-36 days after hatching. Predation of juveniles occurs at a high rate, which typically gives them an 11 percent annual survival rate, thus marking them as an “early loss” species. Owlets and juveniles remain with their parents until the month of September, when they are still somewhat dependent on them for food. As the birds leave the nests during early September, the survival rate begins to decline rapidly as they become increasingly susceptible to starvation and predators.

Reference

Gutiérrez, R.J., A.B. Franklin, and W.S. Lahaye. 1995. “Northern Spotted Owl.” The Birds of North America (P.G. Rodewald, ed.) Ithaca: Cornell Lab of Ornithology. https://birdsna.org/Species-Account/bna/species/spoowl/introduction. Accessed June 2, 2016.

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Trophic Strategy

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The northern spotted owl is considered to be in the tertiary trophic level, meaning that it feeds on species within the primary and secondary levels. The owls feed on small rodents such as flying squirrels, red tree voles, woodrats, as well as other birds, invertebrates, and reptiles. Because these owls are at the top of their food chain, the stability of species populations in lower trophic levels depends on predation by the owls. However, as a result of habitat destruction due to timber harvesting, northern spotted owls have been steadily decreasing in population in recent decades, especially in Washington State. As a result, species within the trophic levels below have begun to overpopulate, which has created an imbalance. The stability of trophic levels is essential in maintaining healthy ecosystems, which requires preservation of animals such as Strix occidentalis caurina.

References

  • Gutiérrez, R.J., A.B. Franklin, and W.S. Lahaye. 1995. “Northern Spotted Owl.” The Birds of North America (P.G. Rodewald, ed.) Ithaca: Cornell Lab of Ornithology. https://birdsna.org/Species-Account/bna/species/spoowl/introduction. Accessed June 2, 2016.
  • Oregon Fish and Wildlife Office. 2016. “Northern Spotted Owl.” U.S. Fish and Wildlife Service. https://www.fws.gov/oregonfwo/articles.cfm?id=149489595. Accessed June 2, 2016.

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Northern spotted owl

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The northern spotted owl (Strix occidentalis caurina) is one of three spotted owl subspecies. A western North American bird in the family Strigidae, genus Strix, it is a medium-sized dark brown owl native to the Pacific Northwest. An important indicator species, the northern spotted owl remains threatened due to continued population decline from human-caused habitat destruction and competition with invasive species, its main competitor being the barred owl.

Description

Northern spotted owls have dark brown plumage with white spots and no ear tufts. They are typically around sixteen to nineteen inches in length and one to one and one sixth pounds. Females are about 10-20% larger than males. Their wingspan is approximately 42 inches. They are a mainly nocturnal species, and form long-term pair bonds. While most owls have yellow to red-orange colored eyes, northern spotted owls are one of the few owls with darkish to black-colored eyes.

Vocalizations

Thirteen different sounds of hoots, whistles, and barks have been identified to be sounds of the northern spotted owl, with females having higher pitched calls than males. Of the three different styles of calls, hoots appear to be most commonly used to announce things, such as territory and prey. The whistles are often used by the females to present themselves to the males, and the barks during territorial issues between owls.[3]

Distribution and habitat

The northern spotted owl primarily inhabits old growth forests in the northern part of its range (extreme southwestern Canada to southern Oregon) and landscapes with a mix of old and younger forest types in the southern part of its range (Klamath region and California). The subspecies' range is the Pacific coast from extreme southern British Columbia to Marin County in northern California.

Most spotted owls inhabit federal lands (Forest Service, Bureau of Land Management, and National Park Service lands), although significant numbers occur on state lands in Washington, Oregon, and California, as well as tribal and private properties.

Northern spotted owls range on 500,000 acres of the 7.6 percent of private forestlands managed by Native American tribes in the state of Washington. Federally recognized tribes are treated as sovereign governments, and each recognized tribe is responsible for their own management plans for the northern spotted owls in their area. Regardless of tribal or private ownership, however, the United States federal government requires all land owners and inhabitants to comply with the Endangered Species Act.[4]

The northern spotted owl nests in cavities or on platforms in large trees. It will also use abandoned nests of other species. Northern spotted owls remain in the same geographical areas unless forced out from harsh conditions or lack of food.

Diet

The northern spotted owl diet consists of small mammals (91.5%), other birds (4.3%), insects (4.1%), and other prey (0.1%). These prey are most nocturnal (91.9%) or active during the day and night (4.8%), which corresponds to the primarily nocturnal nature of the northern spotted owl.[5] The main species consumed by the northern spotted owl are northern flying squirrels (Glaucomys sabrinus), woodrats (Neotoma fuscipes and N. cinerea), red tree voles (Arborimus longicaudus), western red-backed voles (Clethnonomys californicus), deer mice (Peromyscus maniculatus), and gophers (Thomomys spp.). Consumption of these small mammals varies by habitat region and proliferation of small nocturnal mammals.[5] Recent invasion of barred owls (Strix varia) into the northern spotted owl range has resulted in decreased food availability due to overlap in dietary preferences.[6]

Behavior

The northern spotted owl is intolerant of habitat disturbance. Each nesting pair needs a large amount of land for hunting and nesting, and will not migrate unless they experience drastic seasonal changes, such as heavy snows, which make hunting difficult. Their flight pattern is distinct, involving a series of rapid wingbeats interspersed with gliding flight. This technique allows them to glide silently down upon their prey.[7]

Reproduction

Northern spotted owls reach sexual maturity at two years of age, but do not typically breed until three years of age. Males and females mate in February or March, with the female laying two or three eggs in March or April. Eggs are incubated by the female for around thirty days until hatching. After hatching, the young owls remain in the nest and the adult female provides primary care. Fledgling occurs in 34 to 36 days. The hunting and feeding is done by the male during this time. The young owls remain with the parents until late summer to early fall. They leave the nest and form their own winter feeding range. By spring, the young owls' territory will be from 2 to 24 miles from the parents.[8]

Conservation

Northern spotted owl, Oregon Zoo, Portland, Oregon

There are fewer than 1,200 pairs in Oregon, 560 pairs in Northern California, and 500 pairs in Washington. Washington alone has lost over 90 percent of its old growth forest due to logging which has caused a 40-90 percent decline of the Northern Spotted Owl population.

The worldwide IUCN Red List of Threatened Species status for the spotted owl species is "Near Threatened" with a decreasing population trend. As the IUCN Red List does not track subspecies, this status is applied to species across its whole range in Canada, the United States and Mexico.

The population in British Columbia has become almost extinct. From an original population of at least 1,000, fewer than 100 breeding pairs were left in the 1990s.[9] The Canadian population was declared endangered by the Committee on the Status of Endangered Wildlife in Canada under the 2002 Species at Risk Act, now numbers less than 100 breeding pairs of birds. By 2002 it was 30 breeding pairs, and by 2005 just 22 individuals containing 6 breeding pairs. A captive breeding and release program mooted in 2006 removed 10 individuals from the wild.[9] It started in 2007 in Langley with the goal of producing owls in captivity for release into protected habitat to prevent the extirpation of the species from Canada.[10] The short-term goals of the Program include growing the captive population to 10 breeding pairs and releasing 10-20 offspring per year into the 300,000 hectares of protected old-growth forest. Long-term the Breeding Program aims to recover the wild population to self-sustaining numbers, approximately 300 adults, over the next 10–20 years.

In 2021, there were only 3 individuals left in the wild in Canada.[11] The wild population dwindled down to a single female inhabiting the forests of the Spuzzum First Nation. The captive breeding program saw three males released nearby in August 2022, but one was brought back into captivity after being hit by a train and the other two died of unknown causes in May 2023. The captive breeding population has around 30 individuals.[9]

The northern spotted owl was listed as a threatened species under the Endangered Species Act throughout its range of northern California, Oregon and Washington by the United States Fish and Wildlife Service on June 23, 1990 citing loss of old-growth habitat as the primary threat. The USFWS previously reviewed the status of the northern spotted owl in 1982, 1987 and 1989 but found it did not warrant listing as either threatened or endangered. Logging in national forests containing the northern spotted owl was stopped by court order in 1991.

Controversy

In 1990, the logging industry estimated up to 30,000 of 168,000 jobs would be lost because of the owl's status, which agreed closely with a Forest Service estimate.[12] Harvests of timber in the Pacific Northwest were reduced by 80%, decreasing the supply of lumber and increasing prices.[8] However, jobs were already declining because of dwindling old-growth forest harvests and automation of the lumber industry.[12] One study at the University of Wisconsin–Madison by environmental scientists argued that logging jobs had been in a long decline and that environmental protection was not a significant factor in job loss.[13] From 1947 to 1964, the number of logging jobs declined 90%. Starting with the Wilderness Act of 1964, environmental protection saved 51,000 jobs in the Pacific Northwest.[14]

The controversy pitted individual loggers and small sawmill owners against environmentalists. Bumper stickers reading Kill a Spotted Owl—Save a Logger and I Like Spotted Owls—Fried appeared to support the loggers.[12] Plastic spotted owls were hung in effigy in Oregon sawmills.[15] The logging industry, in response to continued bad publicity, started the Sustainable Forestry Initiative.[16] While timber interests and conservatives have cited the northern spotted owl as an example of excessive or misguided environmental protection, many environmentalists view the owl as an "indicator species," or "canary in a coal mine" whose preservation has created protection for an entire threatened ecosystem.[17]

Protection of the owl, under both the Endangered Species Act and the National Forest Management Act, has led to significant changes in forest practices in the northwest. President Clinton's controversial Northwest Forest Plan of 1994 was designed primarily to protect owls and other species dependent on old-growth forests while ensuring a certain amount of timber harvest. Although the result was much less logging, industry automation and the new law meant the loss of thousands of jobs.[18]

The debate has cooled somewhat over the years, with little response from environmentalists as the owl's population continues to decline by 7.3 percent per year.[19] In 2004 the U.S. Fish and Wildlife Service reaffirmed that the owl remained threatened, but indicated that invasion by barred owls into the range and habitat of the spotted owl was also a cause of declining spotted owl populations.

In 2007, the USFWS proposed a new recovery plan intended to guide all management actions on lands where spotted owls occur, and to aid in recovery of the species. Early proposals were criticized by environmental groups as significantly weakening existing protections for the species. The Obama administration reversed proposals that would have increased logging on Bureau of Land Management administered lands. Recent discussion has been focused on two novel approaches. One of these would emphasize wildfire management as key to owl persistence on the east side of the Cascades, and in the Klamath province. Another proposal, on control of barred owl populations through culling,[20] has been criticized by some animal rights and other activists.[21]

Federal biologists were considering in 2010 whether removal of competing barred owls would allow expansion of spotted owl populations.[22][23][24]

In early 2021, the Trump administration removed more than 3 million acres of Pacific Northwest land from the protected habitat of the northern spotted owl, 15 times the amount it had previously proposed opening to the timber industry. Aurelia Skipwith, director of the Fish and Wildlife Service, stated that "these common-sense revisions ensure we are continuing to recover the northern spotted owl while being a good neighbor to rural communities within the critical habitat" even though northern spotted owl populations continue to decline.[25] This was reversed by the Biden administration in 2021, restoring previous protections.[26]

Influence of barred owl invasion

Population decline of northern spotted owl

The barred owl is an owl species native to the Eastern United States, but has invasively expanded west into the habitat ranges of the northern spotted owl. Invasion of barred owls into the northern spotted owl’s habitat has occurred recently, with all of northern spotted owl territory now also inhabited by the barred owl.[27] Barred owls have a diet of small mammals (74.7%), other birds (8.3%), amphibians (6.4%), bugs (5.6%), crayfish (3.0%), fish (1.5%), reptiles, snails and slugs, and earthworms (<1.0% each).[6] This diet is similar to the northern spotted owl, and the addition of barred owls to the northern spotted owl’s range creates increased competition for food.[5] In the same areas, northern spotted owls require around three to four times more range than barred owls, which places more strain on the northern spotted owls.[6] As barred owl population densities increase, the strain of food competition will worsen for northern spotted owls.

The greater diversity of diet in the barred owl, notably in the amphibians, crayfish, and fish consumed, threatens ecological stability due to extended predation now experienced by affected species. The additional food sources also give an advantage to the barred owl over the northern spotted owl, worsening the northern spotted owl's ability to compete. Paired with more predation of prey that is shared between the barred owl and the northern spotted owl, the introduction of the barred owl in these areas may have unknown long term effects on the ecological balance of these habitats.[28] The most drastic effect is on the northern spotted owl population, which is estimated to have decreased at an annual rate of 3.8% from 1985 to 2013.[29] This population loss is directly related to the presence of barred owls. The Diller et al. (2016) study demonstrated that lethal removal of barred owls resulted in the northern spotted owl populations to increase, while populations of northern spotted owls continued to decrease if barred owl populations were left alone.[29] Should northern owl habitat areas continue to be protected under the Northwest Forest Plan and other related legislation, solutions to regulate barred owl populations could reverse the population decline of the northern spotted owl. Without intervention, continued annual decrease in population levels would ultimately end in extinction of the northern spotted owl.

Hybridization

Northern spotted owls and barred owls have been shown to be capable of producing hybrid offspring. Previous geographical isolation had prevented prior hybridization, and current ones are difficult to distinguish from nonhybrids without using genetic testing techniques. However, of those differences that are discernable, hybrids tend to be larger and lighter colored than northern spotted owls, with similar facial features to barred owls.[30] All hybridization occurred between male northern spotted owls and female barred owls. Cross-breeding amongst the species is a very limited event, and likely insufficient to be significantly detrimental to either species. Direct competition between species for habitat space and food is determined to be much more significant issues in affecting both target populations.[31] There has also been genetic evidence of cross breeding between northern spotted owls and California spotted owls (S. o. occidentalis), but since both are subspecies of the same species, this is not truly considered hybridization.[32]

See also

References

  1. ^ "NatureServe Explorer 2.0". explorer.natureserve.org. Retrieved November 10, 2022.
  2. ^ "Appendices | CITES". cites.org. Retrieved January 14, 2022.
  3. ^ Courtney, Stephen P.; Blakesley, Jennifer A.; Bigley, Richard E.; Cody, Martin L.; Dumbacher, Jack P.; Fleischer, Robert C.; Franklin, Alan B.; Franklin, Jerry F.; Gutiérrez, Rocky J.; Marzluff, John M. & Sztukowski, Lisa (September 2004). Scientific Evaluation of the Status of the Northern Spotted Owl (PDF) (Report). Portland, Oregon: Sustainable Ecosystems Institute.
  4. ^ "WFPA - NSO Conservation in WA - Tribal Forestland". www.northernspottedowl.org. Retrieved February 24, 2016.
  5. ^ a b c Forsman, Eric D.; Bruce, Charles R.; Walter, Mary A.; Meslow, E. Charles (1987). "A Current Assessment of the Spotted Owl Population in Oregon". The Murrelet. 68 (2): 51. doi:10.2307/3535693. ISSN 0027-3716. JSTOR 3535693.
  6. ^ a b c Livezey, Kent B. (September 2007). "Barred Owl Habitat and Prey: A Review and Synthesis of the Literature". Journal of Raptor Research. 41 (3): 177–201. doi:10.3356/0892-1016(2007)41[177:bohapa]2.0.co;2. ISSN 0892-1016.
  7. ^ "Northern Spotted Owl". Defenders of Wildlife. Retrieved October 30, 2008.
  8. ^ a b Brokaw, Jeanne (Nov/Dec 1996). "Does Anybody Give a Hoot?" Mother Jones. Accessed April 3, 2013.
  9. ^ a b c Ruth Kamnitzer (May 18, 2023). "One left: British Columbia's last chance on northern spotted owls". Mongabay. Retrieved May 26, 2023.
  10. ^ Northern Spotted Owl Breeding Program
  11. ^ "How Canada is trying to protect its last three spotted owls". the Guardian. April 16, 2021. Retrieved April 16, 2021.
  12. ^ a b c Satchell, M. (June 25, 1990) U.S. News & World Report, Vol. 108, Issue 25, p. 27.
  13. ^ Freudenburg, William R.; Lisa J. Wilson; Daniel O'Leary (1998). "Forty Years of Spotted Owls? A Longitudinal Analysis of Logging-Industry Job Losses" (PDF). Sociological Perspectives. 41 (#1): 1–26. doi:10.2307/1389351. JSTOR 1389351. S2CID 37523161. Archived from the original (PDF) on August 30, 2006. Retrieved November 12, 2008.
  14. ^ Guglielmino, Janine (Summer 1997). American Forests, Vol. 103, Issue 2, p. 6.
  15. ^ Adams, Larry (December 1999). Wood & Wood Products, Vol. 104, Issue 13, p. 62.
  16. ^ Sustainable Forestry Initiative. aboutsfi.org
  17. ^ "American Lands Alliance Action Alert". Americanlands.org. May 15, 2007. Archived from the original on June 13, 2007.
  18. ^ Knickerbocker, Brad (June 27, 2007). "Northern spotted owl's decline revives old concerns". Christian Science Monitor. Retrieved June 27, 2007.
  19. ^ "How Should We Manage the Barred Owl?" Olympic Peninsula Audubon Society. Accessed April 3, 2013.
  20. ^ Johnson DH, White GC, Franklin AB, Diller LV, Blackburn I, Pierce DJ, Olson GS, Buchanan JB, Thrailkill J, Woodbridge B, Ostwald M. (2008). Study designs for Barred Owl removal experiments to evaluate potential effects on Northern Spotted Owls. Report prepared for the U.S. Fish and Wildlife Service, Lacey, WA and Yreka, CA. Olympia, WA: Washington Department of Fish and Wildlife. 32 p.
  21. ^ Verhovek, Sam Howe (June 4, 2007). "To protect spotted owl, larger rival is targeted". Los Angeles Times.
  22. ^ Barnard, Jeff (December 10, 2009). Experiment to test killing one owl to help another; Barred owl competing against spotted owl. The Associated Press
  23. ^ Livezey KB (2010). "Killing barred owls to help spotted owls I: a global perspective" (PDF). Northwestern Naturalist. 91 (2): 107–133. doi:10.1898/NWN09-37.1. JSTOR 40856470. S2CID 11691153. Archived from the original (PDF) on May 25, 2017.
  24. ^ Livezey KB (2010). "Killing barred owls to help spotted owls II: implications for many other range-expanding species". Northwestern Naturalist. 91 (3): 251–270. doi:10.1898/NWN09-38.1. JSTOR 40983223. S2CID 85425945.
  25. ^ Friedman, Lisa; Einhorn, Catrin (January 13, 2021). "Trump Opens Habitat of a Threatened Owl to Timber Harvesting". The New York Times. ISSN 0362-4331. Retrieved January 14, 2021.
  26. ^ "Victory for spotted owl as Trump-era plan to reduce habitat is struck down". The Guardian. November 10, 2021.
  27. ^ Lewicki, Krista E.; Huyvaert, Kathryn P.; Piaggio, Antoinette J.; Diller, Lowell V.; Franklin, Alan B. (December 20, 2014). "Effects of barred owl (Strix varia) range expansion on Haemoproteus parasite assemblage dynamics and transmission in barred and northern spotted owls (Strix occidentalis caurina)". Biological Invasions. 17 (6): 1713–1727. doi:10.1007/s10530-014-0828-5. ISSN 1387-3547. S2CID 4798840.
  28. ^ Holm, Samantha R.; Noon, Barry R.; Wiens, J. David; Ripple, William J. (November 27, 2016). "Potential trophic cascades triggered by the barred owl range expansion". Wildlife Society Bulletin. 40 (4): 615–624. doi:10.1002/wsb.714. ISSN 1938-5463.
  29. ^ a b Diller, Lowell V.; Hamm, Keith A.; Early, Desiree A.; Lamphear, David W.; Dugger, Katie M.; Yackulic, Charles B.; Schwarz, Carl J.; Carlson, Peter C.; McDonald, Trent L. (February 17, 2016). "Demographic response of northern spotted owls to barred owl removal". The Journal of Wildlife Management. 80 (4): 691–707. doi:10.1002/jwmg.1046. ISSN 0022-541X.
  30. ^ Hamer, Thomas E.; Forsman, Eric D.; Fuchs, A. D. & Walters, M. L. (April 1994). "Hybridization Between Barred and Spotted Owls" (PDF). The Auk. 111 (2): 487–491. doi:10.2307/4088616. JSTOR 4088616.
  31. ^ Kelly, Elizabeth G.; Forsman, Eric D. (2004). "Recent Records of Hybridization Between Barred Owls (Strix Varia) and Northern Spotted Owls (S. Occidentalis Caurina)". The Auk. 121 (3): 806. doi:10.1642/0004-8038(2004)121[0806:rrohbb]2.0.co;2. ISSN 0004-8038. S2CID 86769738.
  32. ^ BARROWCLOUGH, G. F.; GROTH, J. G.; MERTZ, L. A.; GUTIÉRREZ, R. J. (March 16, 2005). "Genetic structure, introgression, and a narrow hybrid zone between northern and California spotted owls (Strix occidentalis)". Molecular Ecology. 14 (4): 1109–1120. doi:10.1111/j.1365-294x.2005.02465.x. ISSN 0962-1083. PMID 15773939. S2CID 23046067.

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Northern spotted owl: Brief Summary

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The northern spotted owl (Strix occidentalis caurina) is one of three spotted owl subspecies. A western North American bird in the family Strigidae, genus Strix, it is a medium-sized dark brown owl native to the Pacific Northwest. An important indicator species, the northern spotted owl remains threatened due to continued population decline from human-caused habitat destruction and competition with invasive species, its main competitor being the barred owl.

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