Northern Spotted Owl
Northern Spotted Owl
Strix occidentalis caurina
|Listed||June 26, 1990|
|Description||Medium-sized, dark brown owl with dark eyes, white spots on head and neck, and white mottling on breast.|
|Habitat||Old-growth and mixed old-growth/mature forest.|
|Food||Small mammals, birds, reptiles, and insects.|
|Reproduction||Clutch of two eggs.|
|Threats||Logging of habitat.|
|Range||California, Oregon, Washington; British Columbia, Canada|
The northern spotted owl, one of three spotted owl subspecies, is a medium-sized owl with a round head, dark brown plumage, and dark eyes. It has white spots on the head and neck and white mottling on the breast and abdomen. The female is slightly larger than the male and has a higher pitched call. Juveniles go through a series of downy plumages in their first summer; afterwards they are distinguishable from adults only by ragged white downy tips on their tail feathers.
The northern spotted owl is distinguished from the two other subspecies—the California spotted owl (Strix occidentalis occidentalis ) and the Mexican spotted owl (S. o. lucida )—by slight differences in plumage and their respective geographic ranges. The Mexican spotted owl was proposed for listing as threatened in November 1991.
The northern spotted owl inhabits a relatively large home range, which it uses for nesting, foraging, and roosting. It usually spends the entire year on its territory.
Like most other owls, it is primarily nocturnal, swooping down from perches to take prey. Its diet consists mostly of small mammals, but also includes birds, reptiles, and insects. The most important prey are flying squirrels (Glaucomys sabrinus ), red tree voles (Arborimus longicaudus ), and dusky-footed woodrats (Neotoma fuscipes ).
Owl pairs do not nest every year, and not all nesting attempts are successful. It is believed that nesting patterns may be related to local prey availability. Nesting behavior begins in February and March, and nests are located almost exclusively in tree cavities or platforms. Pairs do not build their own nest but use cavities at the broken tops of old-growth conifers, nests built by other birds or mammals, and naturally occurring platforms. Females lay a clutch of two eggs in March or early April, and incubate them for about 32 days. The male feeds the female and young during incubation and brooding. The young leave the nest after about a month and remain near the nest where they are fed by the adults until early fall. The young disperse in September or October.
Young northern spotted owls have a much higher mortality rate than adult birds. Studies have found that only about 19% survived their first year. The principal causes of juvenile death appeared to be starvation and predation by great horned owls.
The northern spotted owl inhabits old-growth forests or mixed stands of old-growth and mature trees. Pairs establish extensive territories, which are used for nesting, foraging, and roosting. The sub-species is occasionally found in younger forests that have remnant patches of large trees or scattered individual large trees. Old-growth forests possess a combination of characteristics required by the owl: a high, multistory canopy dominated by large trees; numerous trees with cavities or broken tops; woody debris or fallen trees; and open space beneath the canopy for flying.
The size of a pair's home range varies across the subspecies' geographical distribution. The median size of a pair's home range is about 10,000 acres (4,050 hectares) for the Olympic Peninsula; 6,300 acres (2,550 hectares) for the Washington Cascades; 3,000 acres (1,200 hectares) for the Oregon Cascades; 4,800 acres (1,950 hectares) for the Oregon Coast Range; and 3,300 acres (1,350 hectares) for the Klamath Provence.
The precise historic range of the northern spotted owl cannot be known with certainty. Early European settlers began cutting the old-growth forests, particularly in coastal and foothill areas, before the owl's range was determined. Researchers generally believe that the owl inhabited all suitable habitat from southern British Columbia to northern California. There are no historic population estimates.
Northern spotted owls are found in what old-growth forest remains throughout the subspecies' historic range. By the late twentieth century, most privately owned old-growth forest had been cut; approximately 90% of the remaining old-growth forest was on federal land managed by the U. S. Forest Service, U. S. Bureau of Land Management (BLM), and the National Park Service. The early twenty-first century range was from southwestern British Columbia, south through western Washington, western Oregon, and northern California to near San Francisco Bay. The southern boundary that separated the northern spotted owl from the California spotted owl was the Pit River area of Shasta County, California.
Northern spotted owls were not uniformly distributed throughout this range. Most inhabited the Cascades in Oregon and the Klamath Mountains of southwestern Oregon and northwestern California. Densities were lowest in northern Washington, southern British Columbia, and northeastern California. Approximately 2,000 breeding pairs were known, and the total population was estimated to number between 3,000 and 5,000 pairs.
The principal threat to the northern spotted owl is the ongoing reduction of its old-growth forest habitat through logging. Nearly all privately owned old-growth forest has already been cut in the Pacific Northwest, and suitable spotted owl habitat is almost completely confined to federal land. Conflict over forest management practices to conserve the spotted owl date to at least the mid-1970s when wildlife officials in Oregon, in concert with federal scientists, attempted to establish a state management plan for the subspecies.
Conservation and Recovery
The decision to list the northern spotted owl and institute a conservation plan has generated more controversy than any other action taken under the Endangered Species Act in several decades. Citing a threat to the regional economy, companies, organizations, and localities dependent on the timber industry vigorously opposed any action that would reduce the timber cut on federal land in the Pacific Northwest. A coalition of environmental organizations and independent and government scientists has been equally vigorous in pressing for additional protection for the region's old-growth forests which serve as the owl's habitat.
Following a January 1987 petition from a private conservation organization to list the owl, the U. S. Fish and Wildlife Service (FWS) determined in December 1987 that listing the owl was not warranted. The Sierra Club Legal Defense Fund then challenged that decision by filing a lawsuit against the FWS in the U. S. District Court for the Western District of Washington (Northern Spotted Owl v. Hodel, no. C88-573Z). On November 17, 1988, the court found that FWS's failure to list the northern spotted owl was "arbitrary and capricious or contrary to law" and directed the service to reconsider its decision. Following this judicial rebuke, the FWS organized a special listing review team to evaluate the scientific evidence concerning the threat to the owl. In June 1989, the FWS proposed that the northern spotted owl be listed as threatened. The listing was made final on June 26, 1990. Meanwhile the controversy between timber interests and environmentalists had escalated into a major political debate over the health of the local economy versus conservation of the owl and its old-growth forest habitat.
In 1989, while the listing proposal was under consideration, an interagency scientific committee was established to develop a conservation plan for the owl. On April 2, 1990, it issued a report, "A Conservation Strategy for the Northern Spotted Owl" (popularly known as he "Jack Ward Thomas Report," after the committee's chairman). This report recommended the establishment of habitat conservation areas on nearly eight million acres (3.2 million hectares) of federal land throughout the owl's range. The conservation plan called for a network of individual reserves, each large enough to support a minimum of 20 pairs of owls. No logging would be allowed on these reserves, and a strict timber management policy would apply on federal land connecting the conservation areas.
In February 1991, the FWS was ordered by the U. S. district court presiding over Northern Spotted Owl v. Hodel to designate critical habitat for the owl. On May 6, FWS proposed a network of critical habitat areas totaling more than 11 million acres (4.5 million hectares) of federal, state, and private land in Washington, Oregon, and California. These areas were largely based on the habitat conservation areas mapped in the Jack Ward Thomas Report. On August 13, 1991, the FWS revised its proposal to include only federal and state land. It proposed that approximately 8.2 million acres (3.3 million hectares) be designated as critical habitat. The final determination was made on January 9, 1992, when the FWS announced that critical habitat for the owl would encompass approximately 6.9 million acres (2.8 million hectares) of federal land.
The listing of the northern spotted owl as threatened and the determination of its critical habitat has hardly ended the political or legal struggle. On May 23, 1991, a U. S. district judge ordered the suspension of timber sales in the national forests of the Pacific Northwest until the Forest Service produced an effective protection plan for the northern spotted owl.
And on September 30, 1991, Secretary of the Interior Manuel Lujan decided to convene the Endangered Species Committee, sometimes known as the "God Committee," to consider a BLM request for an exemption from the Endangered Species Act. The BLM was seeking permission to sell timber from about 4,000 acres (1,600 hectares) of northern spotted owl habitat. While this was only a small portion of the owl's critical habitat, proponents of protecting the owl regarded this as the first step in a campaign to weaken the provisions of the Endangered Species Act.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
Forsman, E., and E. C. Meslow. 1986. "The Spotted Owl." In Audubon Wildlife Report 1986. Academic Press, San Diego.
Thomas, J. W., et al. 1990. "A Conservation Strategy for the Northern Spotted Owl." U. S. Department of Agriculture, U. S. Forest Service, U. S. Department of the Interior, U. S. Fish and Wildlife Service, U. S. Bureau of Land Management, and National Park Service, Portland.
U. S. Fish and Wildlife Service. 9 January 1992. "Determination of Critical Habitat for the Northern Spotted Owl." Federal Register 57.
"Northern Spotted Owl." Beacham's Guide to the Endangered Species of North America. . Encyclopedia.com. (December 18, 2017). http://www.encyclopedia.com/environment/science-magazines/northern-spotted-owl
"Northern Spotted Owl." Beacham's Guide to the Endangered Species of North America. . Retrieved December 18, 2017 from Encyclopedia.com: http://www.encyclopedia.com/environment/science-magazines/northern-spotted-owl
Northern Spotted Owl
Northern spotted owl
The northern spotted owl (Strix occidentalis caurina ) is one of three subspecies of the spotted owl (Strix occidentalis ). Adults are brown, irregularly spotted with white or light brown spots. The face is round with dark brown eyes and a dull yellow colored bill. They are 16–19 in (41–48 cm) long and have wing spans of about 42 in (107 cm). The average weight of a male is 1.2 lb (544 g), whereas the average female weighs 1.4 lb (635 g).
This subspecies of the spotted owl is found only in the southwestern portion of British Columbia, western Washington, western Oregon, and the western coastal region of California south to the San Francisco Bay. Occasionally the bird can be found on the eastern slopes of the Cascade Mountains in Washington and Oregon. It is estimated that there are about 3,000–5,000 individuals of this subspecies.
The other two subspecies of spotted owl are the California spotted owl (S. o. occidentalis ) found in the coastal ranges and western slopes of the Sierra Nevada mountains from Tehama to San Diego counties, and the Mexican spotted owl (S. o. lucida ) found from northern Arizona, southeastern Utah, southwestern Colorado, south through western Texas to central Mexico.
It is thought that spotted owls mate for life and are monogamous. Breeding does not occur until the birds are two to three years of age. The typical clutch size is two, but sometimes as many as four eggs are laid in March or early April. The incubation period is 28–32 days. The female performs the task of incubating the eggs while the male bird brings food to the newly-hatched young. The owlets leave the nest for the first time when they are around 32–36 days old. Without fully mature wings, the young are not yet able to fly well and must often climb back to the nest using their talons and beak. Juvenile survivorship may be only 11%.
Spotted owls hunt by sitting quietly on elevated perches and diving down swiftly on their prey. They forage during the night and spend most of the day roosting. Mammals make up over 90% of the spotted owl's diet. The most important prey species is the northern flying squirrel (Glaucomys sabrinus ) which makes up about 50% of the owl's diet. Woodrats and hares also are important. In all, 30 species of mammals, 23 species of birds, two reptile species, and even some invertebrates have been found in the diets of spotted owls.
Northern spotted owls live almost exclusively in very old coniferous forests. They are found in virgin stands of Douglas fir, western hemlock, grand fir, red fir, and areas of redwoods that are at least 200 years old. They favor areas that have an old-growth overstory with layers of second-growth understory beneath. The overstory is the preferred nesting site and the owls tend to build their nests in trees that have broken tops or cavities, or on stick platforms. In one study, 64% of the nests were in cavities, and the remainder were on stick platforms or other debris on tree limbs. All of the nests in this study were in conifers, all but two of which were living.
Little is known about what features of a stand are critical for spotted owls. The large trees that have nest sites may be important, particularly those producing a multi-layered canopy in which the owls can find a benign microclimate . A thick canopy may be critical in sheltering juvenile owls from avian predators, whereas the understory may be important in providing a cool place for the birds to roost during the warm summer months.
Because of this subspecies' dependence on old-growth coniferous forests and because it feeds at the top trophic level in the old-growth forest food chain/web , it is considered an "indicator species." Indicator species are used by ecologists to measure the health of the ecosystem . If the indicator species is endangered, then it is likely that scores of other species in the ecosystem are just as endangered.
The owls are nonmigratory, with dispersal of young being the only regularly observed movement out of established home ranges. The home range size of spotted owls varies from an average of 4,200 acres (1,700 ha) in Washington to about 2,000 acres (800 ha) in California. In 1987, a team of scientists recommended that in order to be reasonably sure of the species' survival that habitat for 1,500 pairs be set aside. This would necessitate preserving 4–5 million acres (1.5–2 million ha) of old-growth forests—most of what remains.
Unfortunately for these owls, old-growth forests are a scarce habitat which is commercially valuable for timber. Because of the demand for old-growth timber these birds have been the center of controversy between timber interests and environmentalists. The declining numbers of owls alarm preservationists who want old-growth forests set aside to protect the owls, while the loggers feel it is in the public's best interest to continue to cut the economically valuable old-growth timber. Timber companies claim that 12,000 jobs will be lost along with about $300 million annually if felling is restricted.
It has been argued that since old-growth forests are being destroyed, these jobs and revenue will be lost eventually anyway. It has also been argued that the U. S. Forest Service , which manages most of the remaining old-growth forests, subsidizes the timber industry by building expensive access roads and selling the timber at artificially low prices. Environmentalists suggest that the social costs associated with not cutting old growth could be mitigated by redirecting these monies to retraining programs and income supplements.
In 1990, the northern spotted owl was designated by the U. S. Fish and Wildlife Service as a "threatened species." This requires that the owl's habitat be protected from logging . Although the decision to list the spotted owl as "threat ened" did not affect existing logging contracts, timber companies are trying to avoid compliance with the decision. Specifically, they are trying to persuade the President and Congress to revise the Endangered Species Act to allow consideration of economic impacts or to make a specific exception for some or all of the spotted owl's habitat. Currently, under certain circumstances, economic factors can take precedence over biological criteria in deciding whether it is necessary to comply with habitat protection measures. In these cases a special seven-person interdisciplinary committee can assess the economic impacts of protecting the habitat and circumvent the Endangered Species Act if they believe it is warranted. President Bush's Secretary of Interior Manuel Lujan convened the committee to consider allowing logging in spotted owl habitat on some Bureau of Land Management lands.
A team of scientists appointed by the federal government to study the situation recommended that the annual harvest on old-growth forests be reduced by 47%. However, former President George Bush rejected this recommendation and instead proposed that harvest be reduced by 21%. This angered both the environmentalists and the timber industry and the two sides became deadlocked. In the meantime, spotted owl policy is being determined by federal judges rather than biologists. For example, it was a court order that forced the U. S. Fish and Wildlife Service to identify 11.6 million acres (4.7 million ha) as critical habitat . In 1991, a federal judge issued an injunction stopping all new timber sales in areas where the spotted owls live on national forest land. The judge also mandated that the Forest Service produce a conservation plan and Environmental Impact Statement by March 1992. This controversy continued into the presidency of Bill Clinton who convened a Forest Summit in Portland, Oregon on April 2, 1993, to gather information from loggers and environmentalists. Following the summit President Clinton asked his cabinet to devise a balanced solution to the old-growth forest dilemma within 60 days.
Ultimately the fate of the northern spotted owl will be decided in the court rooms and halls of government, where environmentalists and timber interests continue to battle. It is important to realize that the dispute is not merely over one species of owl. The spotted owl is just one of many species dependent on old-growth forests, and may not be in the greatest danger of extinction . As an indicator of the prosperity of old-growth ecosystems in the Pacific Northwest, though, its survival means continued health for the entire biological community .
[Ted T. Cable ]
Hunter Jr., M. L. Wildlife, Forests, and Forestry. Englewood Cliffs, NJ: Prentice-Hall, 1990.
"Northern Spotted Owl." Beacham's Guide to the Endangered Species of North America. Farmington Hills, MI: Gale Group, 2001.
Casey, C. "The Bird of Contention." American Forests 97 (1991): 28–68.
"Northern Spotted Owl." The Sierra Club. [cited May 2002]. <http://www.sierraclub.org/lewisandclark/species/owl.asp>.
"Northern Spotted Owl." Environmental Encyclopedia. . Encyclopedia.com. (December 18, 2017). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/northern-spotted-owl
"Northern Spotted Owl." Environmental Encyclopedia. . Retrieved December 18, 2017 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/northern-spotted-owl