NATURAL HISTORY

NORTHERN SPOTTED OWL } Strix occidentalis caurina
FAMILY: Strigidae

DESCRIPTION: The northern spotted owl is a medium-sized, dark brown owl with a barred tail; white spots on its head, neck, and back; and dark brown eyes surrounded by a large, heart-shaped facial disk. It is the largest of the three spotted owl species and measures 18 to 19 inches in length with a 40-inch wingspan. Females are about 15 percent larger than males and weigh between one and two pounds. Though similar to the barred owl, the northern spotted owl is slightly smaller and darker overall.

HABITAT: Northern spotted owls rely on intact stands of old-growth forest and the particular structures and characteristics found within them, such as high canopy enclosure, large accumulations of woody debris, snags, and tree deformities. Trees with broken tops, deformed limbs, and sizable holes are often used for nesting sites.

RANGE: Northern spotted owls are found from southwestern British Columbia through the Cascade Mountains, coastal ranges, and intervening forested lands of Washington, Oregon, and California, extending as far south as Marin County.

MIGRATION: The sedentary spotted owl does not migrate but may react to variations in temperature by moving up and down within the canopy as well as to lower elevations to survive harsh winters.

BREEDING: Spotted owls usually wait to breed until they reach two to five years of age, though they are sexually mature earlier. Courtship between monogamous pairs begins in early spring, but most nesting pairs do not nest every year. Females generally nest in tree cavities and lay a clutch of two or three eggs that hatch after 30 days. The owls are highly invested in their young and spend much time and effort caring for and teaching chicks to hunt. Juveniles leave their parents to establish their own nesting sites in autumn, traveling 10 to 15 miles from their place of birth.

LIFE CYCLE: Northern spotted owls are believed to live 10 years.

FEEDING: Flying squirrels are a favorite treat of northern spotted owls living in Washington and Oregon, while further south, dusky-footed wood rats are the delicacy of choice. Other prey species include deer mice, tree voles, gophers, and snowshoe hares. Primarily nocturnal, spotted owls are also opportunistic feeders during daytime hours. Northern spotted owls are extremely territorial and require large foraging areas, sometimes of more than 15 square miles.

THREATS: The primary threat to the species’ survival is habitat loss and forest fragmentation due to runaway old-growth forest logging. Other dangers include competition with barred owls, whose range has expanded from the eastern United States to the Pacific Northwest, as well as urban development and disease.

POPULATION TREND: A once-common resident of old-growth forests, the northern spotted owl was scraping by on just 12 percent of its former habitat by 1990. Before the species’ official designation as threatened, annual logging rates on national forests in Oregon were so extreme that the Bureau of Land Management estimated that suitable northern spotted owl habitat would be eliminated within 26 years. No more than 2,500 breeding pairs of northern spotted owls are believed to remain in the United States today.

Photo by John and Karen Hollingsworth, USFWS