By Kari Kirschbaum
Geographic Range
Snowy owls have a circumpolar distribution. They breed in coastal Alaska, Canada, and Greenland, as well as in northern Scandinavia, Russia, southern Novaya Zemlya and northern Siberia. In winter, snowy owls can be found in Canada and the northern United States, sporadically further south into the U.S., in Iceland, the British Isles, northern Europe, central Russia, northern China and Sakhalin. While typically found in the arctic, periodic irruptions of "excess populations" occasionally move south, driven by a lack of food resources in the tundra. Snowy owl fossils have been found as far south as the Tropic of Cancer, and are believed to have originated in that region. (Encyclopedia Britannica, 1995; Hoyo, Elliot, and Sargatal, 1999; National Geographic, 1999; Parmelee, 1992)
Biogeographic Regions:
nearctic 
(native ); palearctic (native ).
Other Geographic Terms:
holarctic .
Habitat
(984 ft)
Snowy owls inhabit open tundra, usually from sea level to less than 300 m elevation. They may also inhabit lowland salt grass meadows and poorly drained freshwater wet meadows, especially for hunting. When food is scarce, snowy owls travel south to warmer climates in winter. Prime winter habitat in the Great Plains is similar to their breeding habitat. In the south, they are frequently seen in villages and urban centers, as well as in marshes and on dunes. (Parmelee, 1992)
These animals are found in the following types of habitat:
temperate ; polar ; terrestrial .
Terrestrial Biomes:
tundra ; desert or dune ; savanna or grassland .
Wetlands: marsh .
Other:
urban ; suburban ; agricultural .
Physical Description
(51.04 to 56.32 oz)
(24.8 to 28.74 in)
(66.93 in)
Snowy owls are the largest bird species in the arctic, 63 to 73 cm long with an average wingspan of 170 cm. Females are larger and heavier than the males, weighing 1550 to 1600 grams, compared to males which weigh 1450 to 1500 grams. Snowy owls are predominantly white with dusky brown spots and bars. Females tend to have more markings than males, which may become nearly completely white as they age. Young snowy owls are generally darker and more heavily marked than adults. Snowy owls have yellow eyes and their legs and feet are covered in white feathers that protect them from the cold weather. (Grzimek, 1972; Kielder Water Bird of Prey Centre, 1999; Living Planet, 1999; Parmelee, 1992)
Some key physical features:
endothermic ; bilateral symmetry .
Sexual dimorphism: female larger, sexes colored or patterned differently.
Reproduction
Snowy owls breed once annually if sufficient prey are available.
Snowy owls breed between May and September.
Snowy owls are generally monogamous, though polygyny has been reported in a few instances when prey was excessively abundant. Breeding pairs may form on the wintering ground or after the owls reach the breeding ground in late April or early May. There is no evidence that pair bonds last beyond one breeding season.
Elaborate courtship displays are associated with breeding pair formation and early breeding activities. The male performs an “aerial display” followed by a “ground display’. The “aerial display” consists of an exaggerated undulating flight, frequently while carrying a lemming in the bill or claws, followed by a gradual climb and finally a gentle vertical descent to the ground. Once on the ground, the male performs the “ground display”. With his back toward the female, the male stands erect and then leans forward with his head lowered and tail partly fanned until he is nearly lying on the ground. Another infrequently observed display is the passing of a lemming from male to female while in flight. (Parmelee, 1992)
Mating systems:
monogamous .
Snowy owls usually breed between May and September. Individuals arrive on the breeding grounds beginning in late April, though breeding pairs may form earlier on the wintering grounds. The male of a pair establishes a territory, and the female selects a nest site, which is a low windswept prominence, such as a hillock, hummock or boulder. The female constructs a nest by scraping out a shallow bowl in the turf or bare ground. The nest is not lined with any insulating materials. The female then begins laying eggs at 2-day intervals. Clutch size is usually 3 to 11 white eggs, depending on prey availability, but can be as large as 16 when prey are extremely abundant. The female incubates the eggs, beginning with the first egg laid. The chicks hatch asynchronously after 32 to 34 days (average 31.6 days) of incubation. The eggs hatch approximately every other day leading to a wide range in size and age of chicks within a nest. The female broods the chicks until they abandon the nest. Both parents feed and protect the chicks, which are covered with snowy white down. The male brings food to the nest, where the female dissects it into smaller pieces to feed to the chicks. Chicks begin to leave the nest before they can fly, 14 to 26 days after hatching. The parents continue to feed them for 5 to 7 weeks until they are able to hunt for themselves.
The age of sexual maturity is not known for this species, though it is likely to me at least two years old. Adult snowy owls are able to breed annually if prey abundance allows. In years of low prey abundance, snowy owls forgo breeding. Snowy owls generally raise only one brood per breeding season. However, if a nest fails early in the breeding season, snowy owls may re-nest. (Parmelee, 1992)
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous .
Snowy owl females lay and incubate the eggs for an average of 31.6 days. After hatching, the female broods the semialtricial chicks until they leave the nest at age 14 to 25 days. Both parents defend the nest by dive-bombing potential predators that approach the nest and using distraction displays to draw the predator away from the nest. The male brings food to the nest for the chicks. The female processes the food by tearing it into smaller pieces before feeding it to the chicks. After the chicks leave the nest, both parents continue to feed and protect the chicks for 5 to 7 weeks. (Parmelee, 1992)
Parental investment:
altricial ; pre-fertilization (provisioning, protecting: female); pre-hatching/birth (protecting: male, female); pre-weaning/fledging (provisioning: male, female, protecting: male, female); pre-independence (provisioning: male, female, protecting: male, female).
Lifespan/Longevity
[External Source: Max Planck Institute for Demographic Research]
[External Source: Max Planck Institute for Demographic Research]
The oldest known snowy owl lived at least 28 years in captivity. The oldest known wild snowy owl lived at least 9 years and 5 month. (Parmelee, 1992)
Behavior
Snowy owls are generally solitary and territorial. Males establish territories on the breeding grounds and defend them using vocalizations and threat postures. Territory size varies with prey abundance; during years of abundant prey, as many as five pairs may hold territories within a square mile whereas pairs are much more widely spaced during years of scarcity. During the winter, females establish territories, which they defend until spring, when they fly north.
Snowy owls are migratory. However, migration in this species is unpredictable and likely related more to prey abundance than seasons or weather. In general, snowy owls move nomadically, and breed when and where prey is abundant. Approximately every four years, many snowy owls irrupt into the northern United States during the winter, presumably because prey is scarce further north.
Unlike most owls, snowy owls are largely diurnal. (Parmelee, 1992)
Home Range
There is no information available regarding the home range of snowy owls. (Parmelee, 1992)
Communication and Perception
Snowy owls utilize sight, sound and touch to communicate and perceive their environment. Males “hoot” more frequently than females, and seem to use this vocalization in territorial defense and establishment. Males and females also give a variety of other calls, including a “rick, rick, rick”, a “kre kre kre”, a mewing and a hiss. These vocalizations are frequently used when the adult is disturbed near the nest.
Physical displays are frequently used to communicate. For example, males use courtship displays to attract a mate (See Mating Systems), and exaggerated posturing when threatened or when defending a territory from a neighboring male. (Parmelee, 1992)
Food Habits
Snowy Owls are carnivorous. They hunt by utilizing an elevated perch that affords them good visibility while waiting for potential prey to appear in the hunting area. Visual scanning of the hunting area is facilitated by their ability to swivel their head three quarters of the way around (270 degrees). Snowy Owls' main foods are typically lemmings and mice. However, they also take rabbits (family Leporidae), seabirds, and fish opportunistically. If extra food is captured, snowy owls may store it on a nearby perch. (Chinery, 1992; Parmelee, 1992)
Primary Diet:
carnivore (eats terrestrial vertebrates).
Animal Foods:
birds; mammals; fish.
Foraging Behaviors:
stores or caches food .
Predation
- humans (Homo sapiens)
- foxes (Canidae)
- jaegers (Stercorarius)
Humans are probably the most important predator of snowy owls. Snowy owls are killed by humans for food, trophies, and to protect game animals. Other predators include foxes, jaegers, and probably dogs, wolves and other avian predators.
Males defend the nest by standing guard nearby while the female incubates the eggs and broods the young. Both sexes attack approaching predators, dive-bombing them and engage in distraction displays to draw the predator away from the nest. (Parmelee, 1992)
Ecosystem Roles
Snowy owls affect the populations of animals that they eat. For example, one owl may consume more than 1,600 lemmings in a year. Snowy owls also compete with many other species for lemmings and other prey. Rough-legged hawks, golden eagles, peregrine falcons, gyrfalcons, jaegers, glaucous gulls, short-eared owls, common ravens, gray wolves, arctic foxes, and ermine are some of the species that compete with snowy owls for prey. Some species, including greater and lesser snow geese (Anser caerulescens) nesting near snowy owl nests seem to benefit from the protection of snowy owls that drive competing predators out of the area. (Parmelee, 1992)
- greater and lesser snow geese (Anser caerulescens)
Economic Importance for Humans: Negative
Snowy owls have been known to raid traplines set out by trappers. Over time they have learned to follow these traplines regularly, costing trappers game animals. (Grzimek, 1972; Hoyo, Elliot, and Sargatal, 1999)
Economic Importance for Humans: Positive
Snowy owls play a part in controlling populations of lemmings and other rodents. However, given their arctic distribution, this has little economic effect on humans. (Grzimek, 1972)
Ways that people benefit from these animals:
controls pest population.
Conservation Status
IUCN Red List: [link]:
Least Concern.
US Migratory Bird Act: [link]:
Protected.
US Federal List: [link]:
No special status.
CITES: [link]:
Appendix II.
State of Michigan List: [link]:
No special status.
The global population of snowy owls is estimated at about 290,000 individuals, and appears to be stable. This species is classified as a species of “least concern” by the IUCN red list, and is not considered endangered or threatened in the United States. It is protected under the U.S. Migratory Bird Act and CITES Appendix II. The most common causes of mortality of snowy owls include collisions with vehicles, utility lines and airplanes, gunshot wounds, electrocution and entanglement in fishing tackle. (BirdLife International, 2004; Parmelee, 1992)
Other Comments
Snowy owls are typically diurnal (active during the day). This distinguishes them from most other owls, which are nocturnal. (National Geographic, 1999)
Contributors
Kari Kirschbaum (author, editor), Animal Diversity Web Staff.
Rebecca Atkinson (author), Fresno City College.
Carl Johansson (editor), Fresno City College.
