Spotted Owl - Strix occidentalis
Calls - Strix occidentalis
Introduction: The Spotted Owl is a medium-sized, darkly coloured, nocturnal woodland owl with a round head and dark brown eyes. The Latin word "occidentalis" refers to something from the west. Other local names include Canyon Owl, Brown-eyed Owl, Wood Owl, and Hoot Owl.
[For help with terms used in the description, see parts of an owl. For general characteristics common to most owl species, see owl physiology.]
Description: The facial disc is pale buffish-brown with some darker concentric lines and a dark rim that is not very prominent. The crown is dark brown, slightly tinged rufous with whitish flecks and small spots. Eyes are blackish-brown. The cere is yellowish-horn and the bill pale greenish-yellow.
Upperparts are dark brown with many transverse or arrow-shaped white spots. Some scapulars have relatively large areas of white, and are dark barred on the outer webs. Flight feathers are barred light and dark with fine vermiculations on the light bars. Tail feathers are dark brown with several narrow whitish bars and a whitish terminal band. The throat is whitish. The upper breast is barred whitish and dark brown, while the lower breast and belly are boldly marked dark brown and white. Individual feathers in this region are dusky at the base, along the shaft, and bordering the tip, with a large rounded white spot at each side of the central streak. This gives the owl its white spotted appearance to the underparts. The belly is boldly barred dark brown and white.
Tarsi are densely feathered to the toes, which are bristled, and coloured pale greyish-brown with yellowish soles. Claws are dusky horn.
Size: Length 40.5-48cm. Wing length 301-328mm. Tail length 191-226mm. Weight 520-760g. Females are heavier than males.
Habits: Spotted Owls are nocturnal. They are placid, often allowing close approach by humans and may be
reluctant to fly. In flight, they have heavy methodical wing beats, but appear buoyant for
their size. When roosting, a Spotted Owl will sit on a branch, near the trunk, where it is
camouflaged against tree bark and shadows.
Voice: The typical advertisement call is a mellow,
4-note hoot, "Whoop wu-hu hoo". Both Males and Females
use it as a territorial call and mate-locating call. During territorial disputes, they
give a more excited version of the call. Other calls are the "series location
call", a series of 7 to 15 hoots, given during disputes and/or calls between paired
birds. A "bark series" of 3 to 7 loud, rapid barks, usually given by the female
during territorial squabbles, and then there is the "nest call" given during the
pre-nesting period. Other sounds given when alarmed include grunts, groans, and chatters.
The female often emits a loud "co-weeep" to contact
Hunting & Food: Hunting is done mainly at night,
usually beginning just after sunset and ending a half hour before sunrise. Spotted Owls use
a perch to "sit and wait" to dive down onto prey. They rarely forage in flight.
Prey is sometimes cached for later use. Prey taken to the nest by the male is often
decapitated first. During the day, a Spotted Owl may take the odd prey that passes by its
day roost, fly to a food cache, or fly to a nearby stream to drink. Spotted Owls feed
mainly on flying squirrels and wood rats. Other major prey include gophers, rabbits and hares. Summer diets are more
varied with deer mice and voles being important foods. Spotted Owls are known to capture
30 mammal species including bats, and 23 bird species as prey. They also eat snakes,
crickets, beetles, and moths. They have been known to walk around campgrounds at night to
pick up scraps of food.
Pellets are large and compact measuring about 5.1-7.6 cm in
Breeding: The breeding season is from March to September.
Timing and success in producing offspring are strongly linked to the availability of prey,
and not all pairs breed every year. Spotted owl pairs mate for life, but a new mate is
readily taken if the other disappears. They probably begin breeding at two to three years
Spotted Owls nest primarily in stick nests of Northern Goshawks, on clumps of mistletoe,
in large tree cavities, on broken tops of large trees, on large branches, or cavities in
banks and rock faces. Old nests are not repaired before eggs are laid, and tend to be
reused year after year. Clutch size ranges from 2 to 4 eggs, but averages 2 to 3 eggs.
Eggs are laid every 3 to 4 days, usually in April. The female does all incubation and the
male delivers food to the nest. The incubation period is about 28 to 32 days. Unlike most
other owls, Spotted Owls may not defend their eggs and young from predators, watching
nearby as the nest is destroyed. Young are brooded constantly by the female for 2 weeks,
then she begins to hunt as well. The male brings food to the nest and passes it to the
female to feed to the young. Young start roaming from the nest onto nearby branches at
about 5 weeks, but some flutter to the ground before climbing up into trees. They can fly
weakly at about 6 weeks. At 9 to 10 weeks young can capture insect prey by themselves.
Families remain loosely associated during summer before young disperse in the autumn.
Adults tend to remain near their traditional nesting territories, while juveniles disperse
widely, as much as 100 to 200 km.
Mortality: Spotted Owls are long-lived, with captive
Owls of 21 years being known.
Mortality in the wild is thought to be very high (60 to 95%) for juveniles, especially
during the dispersal stage. Adult mortality is estimated at 5 to 20% annually. 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. Many juveniles starve to death.
It is thought that Barred Owls will out-compete Spotted Owls for habitat, by being more
aggressive, when the two species come into contact.
The Spotted Owl may be the most publicised of all endangered species in North America.
Because of its dependence on large tracts of old-growth coniferous forests, management for
this owl has caused tremendous turmoil in the forest harvesting industry, and has spawned
an incredible amount of research - too much to go into here.
Habitat: The Spotted Owl is a bird of dense, dark, old-growth or mixed
mature and old-growth coniferous forests. Forests are usually dominated by firs or
Douglas-fir, but they also use mature hardwood forests of cottonwoods, alders, oak, and
sycamore, especially along steep-walled river valleys. They prefer an uneven and
multi-layered canopy. They prefer shaded mountain slopes and canyons over
flat plateau areas.
Distribution: North America -
Resident in the mountains and in the humid coastal forest from southwestern mainland
British Columbia south through western Washington and western Oregon to southern
California; and in the Rocky Mountain region of the interior from southern Utah and
southwestern and south-central Colorado south through the mountains of Arizona, New
Mexico, and extreme northwestern Texas. The Spotted Owl is generally non-migratory, except
that some downslope movement from mountains may occur in winter.
Distribution of the Spotted Owl Strix occidentalis
Status: Uncertain. Locally threatened by forest destruction, and by hybridisation with the Barred Owl Strix varia.
Original Description: Xantus de Vesey, John. 1860. Proceedings of the Academy of Natural Science of Philadelphia (Proc. Acad. Nat. Sci. Philadelphia) 11 (1859): p 193.
S. o. occidentalis,
S. o. caurina,
S. o. lucida,
S. o. juanaphillipsae
Campbell, Wayne. 1994. "Know Your Owls". Axia Wildlife
Page compiled by Deane Lewis. Page last updated 2013-07-24
OwlPages.com Owl Species ID: 130.070.000