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Sep 07 2011

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Snowy Owl (Nyctea scandiaca)


Snowy Owl

[order] STRIGIFORMES | [family] Strigidae | [latin] Nyctea scandiaca | [authority] Linnaeus, 1758 | [UK] Snowy Owl | [FR] Harfang des neiges | [DE] Schnee-Eule | [ES] Buho nival | [NL] Sneeuwuil

Subspecies

Genus Species subspecies Region Range
Bubo scandiacus NA, EU n

Genus

Members of the genus Bubo are the largest of the owls. Heavily built with powerful talons they are recognisable by their size, their prominent ear-tufts, and their eyes that vary in colour from yellow to brown but are frequently vivid orange. The genus, including the Asian fish owls of the genus Ketupa – now believed to be part of Bubo – comprises of 20 species ranging Eurasia, Indonesia, Africa and the Americas. DNA evidence suggests that the Snowy Owls of Nyctea and the fish owls of Scotopelia are also candidates for inclusion in this genus.

Physical charateristics

Snowy Owls are large owls with yellow eyes and no ear-tufts. Adult males can be nearly pure white, but most have some brown mottling in their feathers. Adult females are generally larger and darker than males; immatures have considerably more brown mottling. In all plumages, Snowy Owls have solid white faces. Like most owls, Snowy Owls have feathered legs and feet, but the feathers on the Snowy Owl’s legs and feet are especially dense. Snowy Owls are well camouflaged for their Arctic breeding grounds, but in winter, when they are seen in Washington, their mostly white bodies show up well against most backgrounds.

Listen to the sound of Snowy Owl

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wingspan min.: 120 cm wingspan max.: 150 cm
size min.: 53 cm size max.: 65 cm
incubation min.: 30 days incubation max.: 33 days
fledging min.: 43 days fledging max.: 33 days
broods: 1   eggs min.: 3  
      eggs max.: 11  

Range

North America, Eurasia : North

Habitat

Snowy Owls inhabit open terrain in all seasons. They nest above the tree line, and when they leave the tundra, they find similar treeless habitat in prairies, agricultural areas, and coastal dunes.

Reproduction

Snowy Owls are mostly monogamous, though compared to most owls, the pair bond is weak, and bigamy has been recorded. The male establishes a territory and attracts a female, which chooses the nest site. The nest, a simple depression with no added material, is typically located on a dry raised area such as a mound, ridge, or hummock. The female lays 3-11 eggs, depending on the abundance of prey. Thus when lemmings are abundant, so are owls. Snowy Owls may not nest in years when lemmings are scarce. Eggs may be laid up to four days apart, and the female begins to incubate as soon as the first egg is laid. The female incubates for 31-33 days, and the male brings her food while she is on the nest. Once the young hatch, the female broods while the male continues to bring food. Brooding lasts until the young leave the nest at about 2-3 weeks. They young can fly at seven weeks and become independent at 9-10 weeks.

Feeding habits

In the far north, Snowy Owls feed almost exclusively on lemmings when they are available. Since lemmings undergo cyclic population booms and busts, when the lemming population crashes, other small mammals such as rabbits, a variety of waterfowl, and even fish and carrion take the lemmings’ place. Snowy Owls wintering in coastal southwestern British Columbia often prey on water birds, especially Bufflehead Ducks and Horned Grebes.

Video Snowy Owl

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Conservation

This species has a large range, with an estimated global Extent of Occurrence of 1,000,000-10,000,000 km2. It has a large global population estimated to be 290,000 individuals (Rich et al. 2003). Global population trends have not been quantified, but populations appear to be stable so the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern.
Nyctea scandiaca is an irregular breeder in Greenland, Iceland, Fennoscandia and arctic Russia, with Europe accounting for less than a quarter of its global breeding
range. Its European breeding population is small (as few as 1,400 pairs), but fluctuated widely between 1970-1990. Although populations continued to fluctuate in most European countries during 1990-2000, the species remained broadly stable overall. Nevertheless, its population size still renders it susceptible to the risks affecting small populations.
This large owl has a circumpolar distribution in open tundra between 60 degrees N and 83 degrees N. Its populations fluctuate widely according to climatic conditions and prey density, which fluctuates periodically. The total European population amounts to between 16 and 244 breeding pair, the Russian population not included. During the winter it moves somewhat to the south, and some birds appear irregularly in Scotland where several breeding cases have been recorded since the 1970’s.
While there is little information available about long-term population shifts or trends, most Snowy Owl breeding areas in North America are remote from human disturbance. Of course increased access to Arctic areas allows more shooting of owls. Winter sightings are increasing in some areas of Washington, perhaps because of the development of large agricultural fields that attract rodents and waterfowl.
Snowy Owl status Least Concern

Migration

Partially migratory and nomadic; also eruptive at intervals. Though morphologically adapted to withstand sub-zero temperatures, prey availability and (possibly) winter darkness limit scope for wintering in high-arctic latitudes. Certainly in Russia majority withdraw from northernmost areas in autumn (though has been found in winter even on Novaya Zemlya), and move to open country further south to scrub tundra, and even to Siberian steppes as in northern Kazakhstan. Otherwise nomadic in Eurasia, dispersing westwards as well as southwards through tundra zone, presumably in response to food availability. Normal European winter range lies north of 60 degrees N, but irrupting birds occur irregularly south to 53-55 degrees N in Scotland, Denmark, north-east plains of Germany, northern Poland, and European Russia, or to c. 48 degrees N in Siberia.

Distribution map

Snowy Owl distribution range map

Literature

Title Diet of Finnish Snowy Owls Nyctea scandiaca
Author(s): A. Hakala, K. Huhtala, A. Kaikusalo, E. Pulliainen & S. Sulkava
Abstract: The Snowy Owl has, during the last 70 years, bred ..[more]..
Source: Ornis Fennica 83:59-65. 2006

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Title First fossil record of the Snowy Owl Nyctea scandiaca (Linnaeus, 1758)(Aves: Strigidae) from Bulgaria
Author(s): Zlatozar BOEV
Abstract: The Snowy Owl is a resident species, spread in the..[more]..
Source: Historia naturalis bulgarica, 9, 1998: 79-86

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Title DAILY TEMPERATURE CYCLES IN BARRED, GREAT-HORNED AND SNOWY OWLS
Author(s): W. R. SIEGFRIED et al
Abstract: This paper reports preliminary data on daily rhyth..[more]..
Source: Condor 77:502

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