Northern Spotted Owl | Research & Encyclopedia Articles

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 12,000jobs 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.

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/lewis andclark/species/owl.asp>.

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