Strix occidentalis caurinanorthern spotted owl

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Geographic Range

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

Habitat

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.

Physical Description

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.

Reproduction

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.

Behavior

Each pair of owls need a large amount of land for their nesting and hunting grounds; pairs may occupy up to 40 sq. km (amount depends on the habitat). They are territorial. Northern Spotted Owls do not migrate, but they may shift their ranges slightly in response to seasonal changes. These owls have a distinctive flight pattern, involving a series of quick wingbeats interspersed with gliding flight.

Communication and Perception

Food Habits

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.

Economic Importance for Humans: Positive

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.

Economic Importance for Humans: Negative

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.

Conservation Status

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.

  • IUCN Red List [Link]
    Not Evaluated

Other Comments

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

Contributors

Ann Emiley (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

visual

uses sight to communicate

References

Beacham, Walton. "Spotted Owl- Strix occidentolis caurina." W.W.F. Guide to Endangered species, 1992, pg 1397-1400.

Forsman, E., and E.C. Meslow. 1986. "The Spotted Owl." Audubon Wildlife Report 1986. Academic Press, San Diego, CA. pg 743- 762.

Miller, Tyler. Living in the Environment. Wadsworth Publishing Company, Belmont CA. pg 285, 417.

Gutierrez, R. J., A. B. Franklin, and W. S. Lahaye. 1995. Spotted Owl (Strix occidentalis). Birds of North America, 179:1-28.