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Snowy Owl
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The Snowy Owl (Bubo scandiacus) is a large owl of the typical owl family Strigidae. The Snowy Owl was first classified in 1758 by Carolus Linnaeus, the Swedish naturalist who developed binomial nomenclature to classify and organize plants and animals. The bird is also known in North America as the Arctic Owl or the Great White Owl. Until recently, it was regarded as the sole member of a distinct genus, as Nyctea scandiaca, but mtDNA cytochrome b sequence data (Olsen et al. 2002) shows that it is very closely related to the horned owls in the genus Bubo.
DescriptionThis yellow-eyed, black billed white bird is easily recognizeable. It is 53-65 cm (20-26 inches) long with a 125-150 cm (50-60 in) wingspan. Also, these birds can weigh anywhere from 1.8-3 kg (3.5-6.6 lbs). The adult male is virtually pure white, but females and young birds have some dark scalloping; the young are heavily barred, and dark spotting may even be predominate. Its thick plumage, heavily-feathered feet, and coloration render the Snowy Owl well-adapted for life north of the Arctic Circle.
Snowy Owl calls are varied, but the alarm call is a barking, almost quacking krek-krek-krek-krek; the female also has a softer mewling pyee-pyee-pyee-pyee or prek-prek-prek. The song is a deep repeated gawh. They may also clap their beak in response to threats or annoyances. While called clapping, it is believed this sound may actually be a clicking of the tongue, not the beak.
BehaviourThe Snowy Owl is typically found in the northern circumpolar region, where it makes its summer home north of latitude 60 degrees north. However, it is a particularly nomadic bird, and because population fluctuations in its prey species can force it to relocate, it has been known to breed at more southerly latitudes. During the last ice age, there was a Central European paleosubspecies of this bird, Bubo scandiacus gallicus, but no modern subspecies are recognized.
This species of owl nests on the ground, building a scrape on top of a mound or boulder. A site with good visibility, ready access to hunting areas, and a lack of snow is chosen. Gravel bars and abandoned eagle nests may be used. Breeding occurs in May, and depending on the amount of prey available, clutch sizes range from 5 to 14 eggs, which are laid singly, approximately every other day over the course of several days. Hatching takes place approximately five weeks after laying, and the pure white young are cared for by both parents. Both the male and the female defend the nest with their young from predators. Some individuals stay on the breeding grounds while others migrate.
RangeSnowy Owls winter south through Canada and northernmost Eurasia, with irruptions occurring further south in some years. They have been reported as far south as Texas, Georgia, the American Gulf states, southern Russia, northern China and even the Caribbean. Between 1967 and 1975, Snowy Owls bred on the remote island of Fetlar in the Shetland Isles north of Scotland, UK. Females summered as recently as 1993, but their status in the British Isles is now that of a rare winter visitor to Shetland, the Outer Hebrides and the Cairngorms.
Hunting and dietThis powerful bird relies primarily on lemmings and other rodents for food, but at times of low prey density, or during the Ptarmigan nesting period, they may switch to juvenile Ptarmigan. As opportunistic hunters, they feed on a wide variety of small mammals and birds such as meadow voles and dear mice, but will take advantage of larger prey, frequently following traplines to find food. Some of the larger mammal prey includes mice, hares, muskrats, marmots, squirrels, rabbits, prairie dogs, rats, moles, and entrapped furbearers. Birds include ptarmigan, ducks, geese, shorebirds, Ring-necked Pheasants, grouse, American coots, grebes, gulls, songbirds, and Short-eared Owls. Snowy Owls are also known to eat fish and carrion. Most of the owls' hunting is done in the "sit and wait" style; prey may be captured on the ground, in the air or fish may be snatched off the surface of bodies of water using their sharp talons. Each bird must capture roughly 7 to 12 mice per day to meet its food requirement and can eat more than 1,600 lemmings per year.
Snowy Owls, like many other birds, swallow their small prey whole. Strong stomach juices digest the flesh and the indigestible bones, teeth, fur, and feathers are compacted into oval pellets that the bird regurgitates 18 to 24 hours after feeding. Regurgitation often takes place at regular perches, where dozens of pellets may be found. Biologists frequently examine these pellets to determine the quantity and types of prey the birds have eaten. When large prey are eaten in small pieces, pellets will not be produced.
ConservationThough Snowy Owls have few predators, the adults are very watchful and well equipped to defend against any kind of threats towards them or their offspring. During the nesting season the owls face arctic foxes and swift-flying jaegers and must be very careful not to leave their eggs unattended. Environmental conditions also cause local threats of food shortages, but their ability to be mobile permits them to move to areas were supplies may be more sufficient.
Human activities probably pose the greatest danger to these birds, through collisions with power lines, fences, automobiles, or other structures that impose on their natural habitat. Now, Canadian provincial and territorial regulations have introduced prohibitions of killing of these birds in all parts of Canada, where they are most abundant, but the owls are still used for certain study programs.
This species is an extremely important component to the food web in the tundra ecosystem and during its visits to the south, the Snowy Owl may play a useful role in the natural control of rodents in agricultural regions.
External links- - Cornell Lab of Ornithology
- - South Dakota Birds and Birding
- - USGS Patuxent Bird Identification InfoCenter
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