Description

The spotted owl (Strix occidentalis ) is a secretive bird with a round head and black eyes. Its plumage is predominantly dark brown, with white spots on the head and hind-neck, and a barred breast and abdomen. The adult male has an average weight of 582 grams, and the female 637 grams. This species is non-migratory, and inhabits coniferous old-growth forest from southwestern British Columbia southward to coastal forests in southern California; and from central Colorado south through eastern Arizona, New Mexico and western Texas to central Mexico.

There are three subspecies of spotted owl. These are the Northern spotted owl (Strix occidentalis caurina), the Californian spotted owl (S. o. occidentalis) and the Mexican spotted owl (S.o. lucida). In the northern end of their range, spotted owls are found mostly at lower altitudes, however they are found at up to 2300m in the southern end of their range. Mainland British Columbia represents the extreme northern limit of the spotted owl's range, and the subspecies found in B.C. is known as caurina. The spotted owl has probably always been an uncommon resident in British Columbia. Its present status in Canada is endangered.

Spotted owls live almost exclusively in old growth forest. Specific habitat requirements include uneven aged trees, a multi-layer canopy and an abundance of old, diseased or damaged trees for nesting. Open areas are usually avoided by these owls, although they may occasionally make hunting forays into secondary forest. Spotted owls feed primarily on small, nocturnal mammals, such as the flying squirrel, wood rat and the deer mouse.

When they are not hunting, spotted owls find a place to roost. In summer, these owls roost in the deep shade of the forest understory, protected from rain and exposure to heat and the sun's rays. In winter, spotted owls avoid lower temperatures near the ground, roosting higher in the canopy overstory to make use of the sun's energy. Natural predators of the spotted owl include the great horned owl, which preys on both adults and young; the red-tailed hawk, which preys on young; and the common raven, which may destroy eggs.

The spotted owl nests in natural cavities in trees. Spotted owls choose a nesting hole in a tree surrounded by dense forest and close to a permanent water source. Dense understory vegetation near the nest is also necessary to provide fledgling owls with perches when they first leave the nest. Spotted owls mate for life with the same partner, and begin breeding at two to three years of age. Breeding season timing and success in producing offspring are strongly linked to the availability of prey, and not all pairs breed every year. The breeding season is from March to September.

The female lays two or three eggs, which she incubates for 30 days. Once incubation begins, the male does all of the foraging -- feeding the female while she incubates. After the nestlings are about two weeks old, the female assists the male with foraging, and both adults continue feeding them for a further two to three weeks. By late summer, owlets are quite independent of their parents, dispersing further and further from the nest. In Oregon, where spotted owls have been studied in detail, an average of 1.61 young successfully fledge from each nest. The survival rates of young and adults are unknown, and it is not known whether spotted owls can be successfully bred in captivity.

Northern Spotted Owl Habitat

The range of the northern spotted owl (Strix occidentalis caurina) has been divided into 12 physiographic provinces (USDA/USDI 1994a): the Eastern and Western Cascades, Western Lowlands, and Olympic Peninsula Provinces in Washington; the Eastern and Western Cascades, Coast Range, Willamette Valley, and Klamath Provinces in Oregon; and the Klamath, Coast, and Cascades Provinces in California. The Klamath province was divided into two subprovinces by State--the Oregon Klamath Province and the California Klamath Province--even though the two provinces are part of the same geographic area.

Habitat Characteristics

Northern spotted owls generally have large home ranges and use large tracts of land containing significant acreage of older forest to meet their biological needs. The median annual home range size of a northern spotted owl, which varies in size from province to province, is approximated by a circle centered on an owl site center. Estimated median annual home range sizes represent the area used by half of the spotted owl pairs or resident singles studied to date within each province to meet their annual life history needs.

Home range sizes were estimated by analyzing radio-telemetry home range data from studies conducted on the annual movements of spotted owl pairs, referenced in the 1990 Status Review (1990a) and the Interagency Scientific Committee report (Thomas et al. 1990).

Based on studies of owl habitat preferences, including habitat structure and use and prey preference throughout the range of the owl, spotted owl habitat consists of four components: (1) Nesting, (2) roosting, (3) foraging, and (4) dispersal. Although this habitat is variable over the range of the spotted owl, some general attributes are common to the owl's life-history requirements throughout its range.

The age of a forest is not as important for determining habitat suitability for the northern spotted owl as the structure and composition of the forest. Northern interior forests typically may require 150 to 200 years to attain the attributes of nesting and roosting habitat; however, characteristics of nesting and roosting habitat are sometimes found in younger forests, usually those with significant remnant trees from earlier late-successional stands.

The attributes of superior nesting and roosting habitat typically include a moderate to high canopy closure (60 to 80 percent closure); a multi-layered, multi-species canopy with large overstory trees; a high incidence of large trees with various deformities (e.g., large cavities, broken tops, mistletoe infections, and debris accumulations); large accumulations of fallen trees and other debris; and sufficient open space below the canopy for owls to fly (Thomas, et al. 1990).

Spotted owls use a wider array of forest types for foraging, including more open and fragmented habitat. Habitat that meets the spotted owl's need for nesting and roosting also provides foraging habitat. However, some habitat that supports foraging may be inadequate for nesting and roosting. In much of the species' northern range, large, dense forests are also chosen as foraging habitat, probably because they provide relatively high densities of favored prey, the northern flying squirrel (Glaucomys sabrinus), as well as cover from predators. Because much of the flying squirrel's diet is fungal material, old decadent forests provide superior foraging habitat for owls. In southern, lower-elevation portions of the owl's range, the species often forages along the edges of dense forests and in more open forests, preying on the dusky-footed woodrat (Neotoma fuscipes).

In general terms, suitable habitat means those areas with the vegetative structure and composition necessary to provide for successful nesting, roosting and foraging activities sufficient to support a territorial single or breeding pair of spotted owls. Suitable habitat is sometime referred to as nesting, roosting and foraging habitat.

Although habitat that allows spotted owls to disperse may be unsuitable for nesting, roosting, or foraging, it provides an important linkage among blocks of nesting habitat both locally and over the range of the northern spotted owl. This linkage is essential to the conservation of the spotted owl. Dispersal habitat, at a minimum, consists of forest stands with adequate tree size and canopy closure to provide some degree of protection to spotted owls from avian predators and to allow the owls to forage at least occasionally. Suitable and dispersal habitat vary by province and are described separately under the discussion of each province in the following section.

Northern Spotted Owl Populations on Non-Federal Lands

Due primarily to historic timber harvest patterns, approximately 75 percent of the known rangewide population of spotted owls is centered on Federal lands. Owl site centers on non-Federal lands are usually found in remnant stands of older forest, or in younger forests that have had time to regenerate following harvest. In addition, adjacent forested non-Federal lands can provide foraging and dispersal habitat for owls whose site centers are on Federal lands.

As of July 1, 1994, there were 5,431 known locations, or site centers, of northern spotted owl pairs or resident single owls in Washington, Oregon, and California (located between 1989 and 1993)--851 sites (16 percent) in Washington, 2,893 (53 percent) in Oregon, and 1,687 (31 percent) in California. In Washington and Oregon, owl site centers on non-Federal lands are typically widely scattered. Currently, 1,319 or 24 percent of known owl site centers are located on non-Federal lands--140 in Washington, 342 in Oregon, and 837 in California. Of those in California, 631 or 75 percent of the site centers located on non-Federal lands are located in the California Coast Province, where owls are relatively common in second-growth timber stands. Site centers in the interior provinces of California are typically scattered.

In addition to the site centers located on non-Federal lands in Washington, Oregon, and California, preliminary analyses indicate that there are 151 site centers in Washington, 810 centers in Oregon, and 204 centers in California, located on Federal lands that are dependent upon some percentage of suitable owl habitat on adjacent non-Federal lands to support the owls.

Non-Federal lands in certain portions of the owl's range are still necessary to support and supplement the Federal lands-based owl conservation strategy. While the type of support needed varies depending on local conditions, the three general types of conservation support needed within specially designated areas are:

(1) Habitat on non-Federal lands near Federal reserves where existing owl populations are low to provide demographic support for owl populations. Areas that are needed to provide demographic support for Federal reserves include, in Washington: the western portion of the Olympic Peninsula Province and portions of the Eastern and Western Cascade provinces; and in California: the Cascades Province and the southern portion of the Klamath Province;

(2) Dispersal habitat between Federal reserves, where Federal lands may not be distributed to prevent isolation of populations, or between non-Federal ownerships where the distance between reserves is not great. Where distances are large, scattered breeding sites may be important to improve connection between populations. Areas that can provide valuable dispersal habitat on non-Federal lands include, in Washington--the western portion of the Olympic Peninsula Province and portions of the Eastern and Western Cascade Provinces; and in California--the Coast and Cascades Provinces and small portions of the Klamath Province; and

(3) Suitable habitat for breeding populations in areas where Federal ownership is limited. In these areas, functioning spotted owl populations are desired to maintain a widely distributed population of owls. Areas where non-Federal owl populations are believed to play an important role in this regard include, in Washington--the western portion of the Olympic Peninsula Province; and, in California--the Coast and Cascades Provinces.

Dependence on Old-Growth Forest

The northern spotted owl depends on old-growth forests for its hunting and mating territory. The towering trees, some more than 500 years old, form a high protective canopy and provide habitat for animals that are rarely found anywhere else in the world. Some of these animals, such as the red tree mole, are valuable prey for he owl.

An individual spotted owl needs more than 3,000 of old growth to survive, due to its scarce food supply. Because the spotted owl can live only in the old-growth forest environment, it is considered an indicator species. The health of the spotted owl indicates the health of the old-growth forest ecosystem. When an old-growth forest has been clear-cut and converted into a less biologically diverse second-growth forest, the owl's habitat is destroyed, and its numbers dwindle.

Listed as "threatened" under the Endangered Species Act, the owl has inadvertently landed in the middle of a complicated debate over logging in the Pacific Northwest. Under the Act, logging of many old-growth forest has been suspended to protect the bird and its remaining habitat.

Legislation

The U.S. Fish and Wildlife Service listed the northern spotted owl as a threatened species on June 26, 1990, because of the past and continued projected loss of suitable habitat throughout its range. This habitat loss has been caused primarily by timber harvesting, but has been exacerbated by the effects of catastrophic events such as fire, volcanic eruption, and wind storms.

The inadequacy of regulatory mechanisms existing in 1990 under state and Federal law also contributed to the decision to list the northern spotted owl as a threatened species. During the period immediately prior to listing, when the status of the owl was under review, the annual Federal timber harvest in Oregon and Washington averaged approximately five billion board feet per year. Much of that harvest comprised suitable spotted owl habitat. Thus, Federal timber harvest policies at that time contributed significantly to the decline of the owl.

State protection for the owl in 1990 was also inadequate. Since that time, California, Oregon, and Washington have all recognized the plight of the owl and have adopted forest management rules designed to protect this threatened species. The degree of protection accorded the northern spotted owl currently varies under state law. The northern spotted owl is listed under Washington law as an endangered species, under Oregon law as threatened, and under California law as a sensitive species.

On January 15, 1992, the Service designated critical habitat for the northern spotted owl. The critical habitat designation encompassed 6.9 million acres of Federal land in 190 critical habitat units in the states of California, Oregon, and Washington; non-Federal lands were not included in the critical habitat designation. Of the total acreage designated, 20 percent is in California, 47 percent is in Oregon, and 32 percent is in Washington.

Following the April 2, 1993, Forest Conference in Portland, Oregon, President Clinton established a Forest Ecosystem Management Assessment Team (FEMAT) to develop options for the management of Federal late-successional and old-growth forest ecosystems to provide habitat that would support stable populations of species associated with late-successional forests, including the northern spotted owl. FEMAT developed 10 options for the management of late-successional old-growth forest ecosystems on Federal lands in California, Oregon, and Washington. On July 1, 1993, the President identified Option nine as the preferred alternative for amending the Federal agencies' land management plans with respect to Late-successional old-growth forest habitat. It is based on a system of Late-Successional Reserve (LSR)s, riparian reserves, Adaptive Management Areas (AMA)s, and a Matrix of Federal lands interspersed with non-Federal lands.

These designations complemented existing Administratively withdrawn and Congressionally reserved lands.

An underlying premise for the President's selection of the Forest Plan was that Federal lands should carry a disproportionately heavier burden for providing for the conservation of the northern spotted owl, enabling an easing of restrictions on incidental take for the owl on large areas of non-Federal lands. President Clinton thus directed the U.S. Fish and Wildlife Service to issue regulations looking to ease, where appropriate, restrictions on the incidental take of spotted owls on non-Federal lands.

As of 1994 the many issues concerning conservation of precious old-growth forest habitat for the spotted owl continue to linger in the courts. Lawmakers who were eager to settle the issue through legislation have encountered opposition from both the Clinton administration and environmentalist who want the courts to decide the issue. On June 6, 1994 U.S. District Judge Williams L. Dwyer lifted the three year ban on logging however the ruling has been delayed while officials consider the legality of the Clinton plan. The Clinton plan would restrict the amount of timber that could be harvested from forest in western Washington and Oregon and northern California to about 1.1 billion board feet of harvested timber per year. However, environmentalist contend that the plan does not go far enough and have sued the government in order to get even more restrictions on logging while at the same time proponents of the timber industry say that the government has gone to far and are also suing the government. In order for a legislative decision to be reached the government would have to write a management plan that would specify a specific timber harvest level. However in order to avoid a legal challenge the government must include what is called "sufficiency language" in order to meet with the requirements of the 1973 Endangered Species Act. It is the question of this "sufficiency language" that continues to be a major road block in effort to reach a mutually beneficial decision.

A Final Word On the Spotted Owl Issue

With all the issues that surround the spotted owl and the preservation of its precious habitat it is difficult to think that anybody will be able to benefit from all this. However what has spelled disaster for the timber industry has spelled boom for the steel industry. Although steel has long since been used for commercial construction it had never really taken hold in the home construction market. However with the logging freeze to protect the northern spotted owl, wood prices have steadily been steadily increasing, causing many contractors to take a closer look at other alternative building materials. The result was a marked increased in sales of steel frames for homes. However steel is not the only unlikely benefactor from the owl controversy. Other alternative building materials like vinyl, cement and plastics have also seen an increase in sales. Representatives from companies that sale these alternative materials have pointed out that these man-made materials have always had a quality advantage over wood in that there are no threats from termites, warping or rotting, but with the wood market cascading they now have an economic advantage as well.

References

Bart, J. and E.D. Forsman. (1992). Dependence of northern spotted owls (Strix occidentalis caurina) on old-growth forests in the western USA. Biological Conservation, 62, 95-100.

Camia, C. (1994). In spite of pressure, congress leaves owl battle to court. Congressionally Quarterly Weekly Report, 52, 1514.

Carlson, M & Durrer, G. "The Northern Spotted Owl."
URL: http://www.orecity.k12.or.us/ochs/species/SPOTOWL.html (22 Apr. 1998).

Krebs, C. (1994). Ecology. New York: Harper Collins College Publishers.

Irwin, L. "Northern Spotted Owl." Northwest Forestry Association.
URL: http://www.nwtrees.org/spotowl1.html (22 Apr. 1998).

Irwin, L. "Northern Spotted Owl Feeding Owlet." Northwest Forestry Association. URL: http://www.nwtrees.org/spotowl2.html (22 Apr. 1998).

Munk, N. (1994). Thank you, spotted owls. Forbes, 153, 102.

Thomas, J.W., E.D. Forsman, J.B. Lint, E.C. Meslow, B.R. Noon, and J. Verner. 1990. A conservation strategy for the northern spotted owl. Interagency Scientific Committee to Address the Conservation of the Northern Spotted Owl, U.S. Department of Agriculture, Forest Service, and U.S. Department of Interior, Bureau of Land Management, Fish and Wildlife Service, National Park Service, Portland, Oregon.

U.S. tosses "owl" ball back to judg'es court. Wood Technology, 121, 8.

USDA/USDI. (1994a). Final supplemental environmental impact statement on management of habitat for late-successional and old-growth forest related species within the range of the northern spotted owl. Portland, OR. 2 vol.