Snow owl
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Snowy Owl ( Bubo scandiacus ) |
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| Bubo scandiacus | ||||||||||
| ( Linnaeus , 1758) |
The snowy owl ( Bubo scandiacus , syn .: Bubo scandiaca , Nyctea scandiaca , snowy owl ) is a bird - species from the family of real owls (Strigidae), which is one of the characteristic birds of the arctic tundra .
For a long time it was considered the only species of the genus Nyctea and was therefore considered taxonomically isolated from the other owl species. Molecular biological studies have shown, however, that it belongs to the eagle owls ( Bubo ) and is closely related to the great horned owl ( B. virginianus ) and the magellan owl ( B. magellanicus ). The external differences to the eagle owls, such as the white plumage color and the densely feathered feet and toes, can be explained as an adaptation to the arctic habitat.
Appearance
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The snowy owl is almost the size of the eagle owl ( Bubo bubo ). The body length of adult birds is about 55 to 66 cm. As with many other owl species, the males are slightly smaller than the females. On average, they reach a length of 58 cm, while females grow to an average of 63 cm. The same applies to body weight: adult snowy owls weigh between 1.6 and 2.5 kilograms (males on average 1700, females 2100 grams). The wingspan is 145 to 157 centimeters.
The plumage of adult males becomes almost completely white with age. Females and younger birds, on the other hand, have dark spots and ribbons or transverse lines on their white plumage. The young birds have an anthracite gray plumage.
The head of the snowy owl is round. It is noticeable that the black beak is predominantly covered by so-called "vibrissas". These are dense, fine white feathers. The iris of the eyes is colored golden yellow. Similar to the eagle owl, the snowy owl also has feather ears ; However, these are much less pronounced and are rarely straightened. The feet and toes are densely feathered - this dense, snowshoe-like feathering is used for thermal insulation and prevents the owl from sinking into the snow.
voice
Snow owls are very silent outside of the breeding season . During the mating season, on the other hand, the male gives a loud, rough croak and a deep barking “hu” at the breeding site, which serves to attract females and to demarcate the territory . These calls can be heard on the tundra for several kilometers. During this time, the female occasionally lets out a lighter croak that is much quieter. The birds have other sounds in their repertoire. These include hissing noises with which the young owls beg the parent birds for food, cackling " ka.ka.ka " calls as warning calls and gull-like " Kjaa " calls when they are disturbed during brood.
distribution
The snowy owl has a circumpolar distribution and is found in the tundra areas of Iceland , northern Europe , Siberia , Alaska , Canada and Greenland . The southernmost occurrences, for example in Norway , are found in mountains . From 1967 to 1975, snowy owls were breeding in the Shetland Islands .
The snowy owl is a so-called “survival hiker” within its range. That is, it adapts to the respective food supply. Their occurrence depends on the fluctuations in the population of the lemmings , their main prey. In very cold, snowy winters or after a collapse of the lemming population , snowy owls move south to Central Russia , Central Asia , Manchuria and the northern United States . They then occasionally come to northern Central Europe .
With the help of GPS transmitters, it was possible to prove that some animals spend the arctic winter over the frozen arctic sea to hunt waterfowl.
habitat
The snowy owl lives north or above the tree line in clear terrain, for example in bog and heather areas . In the Arctic they overwinter in wind-swept areas of the tundra with little snow , in Scandinavia mainly in the fells . The breeding areas are mostly elevated in areas that are free of snow early.
If they hibernate further south, they stay on agricultural land.
Food and subsistence
Unlike most of the other owls , snowy owls also hunt during the day, mostly from ground-level perches such as boulders, tree trunks, etc. Ä. With their straight flight containing gliding phases, they overcome short distances at low altitudes. If they miss their prey in flight, they run after it and jump up flapping. Since the snowy owl spreads its toes while running, the dense fletching on the legs acts like a snowshoe and enables it to catch up with its prey even in the snow. In very loose snow it also prevents sinking in by spreading its tail and wings. Snow owls also search for hiding spots during their hunt or even try to drive the prey out of their burrows.
Similar to the eagle owl, the snowy owl is an opportunistic hunter who uses everything it can hit as prey. The prey consists mostly of small mammals such as mice , but mostly of lemmings. However, they can certainly prey on animals up to the size of mountain hares and ducks . Hunting for fish and even sea birds has also been observed in coastal areas . The birds beat them in flight, the fishing behavior is still largely unexplored. In very unfavorable feeding conditions, they also hunt the prey from arctic foxes or hen harriers ( kleptoparasitism ) or eat carrion like fish washed up on the coast.
behavior
Specific activity phases cannot be determined for the snowy owl. She prefers to hunt during twilight, but catching prey can be observed at any other time of the day, especially when rearing young. The maximum activity obviously depends on the activity times of the main prey, which is at night for lemmings and during the day for ptarmigan .
As inhabitants of the tundra, snow owls do not seek cover, but usually sit quite exposed on hills, stones or tree trunks. Snow owls often rest for hours without moving, either sitting upright or leaning forward slightly, with their feet and wings being wrapped in loose body plumage. The owls only seek shelter when there is strong sunlight, they stay seated when it rains or snow.
Outside of the breeding season, the owls lead a solitary life and defend their hunting grounds against conspecifics. A loose swarm formation occurs only in extremely difficult winters.
It is assumed that the mating takes place outside of the breeding season, as the arctic summer is extremely short. During the breeding season, the owls are extremely aggressive towards conspecifics and predators; when defending their territory there is fierce fighting between the males in the air and on the ground until the territorial boundaries are determined.
The snowy owl is rather shy of enemies and prefers to avoid them instead of hiding. Due to its position on elevations, it can identify approaching dangers very quickly and react accordingly. Whether the white color has an additional camouflage function is controversial, as the animals are particularly noticeable due to the white plumage, especially during the breeding season in the snow-free season. When defending the nest, the owls have a large repertoire of threatening gestures, ranging from a simple tearing of the beak and ruffling of the plumage to an attack position with raised wings and hissing warning calls. If the threat continues, an attack with claws and beak and in the form of attack flights on the potential enemy takes place.
Reproduction
Courtship and mating
Snow owls are only able to reproduce at the end of their second year of life. They have a seasonal marriage and are largely monogamous during this time . The courtship season begins in the middle of winter. When a female approaches, the male, sitting on the ground, begins making calls and suggesting nest-scratching movements. Then the male performs courtship flights, in which he sometimes flies slowly until it sags downwards. Just before it touches the ground, it lifts itself up again with powerful wing beats. During the courtship flight, the male usually carries a dead lemming in its beak, which it presents to the female at the end of the courtship flight. Singing duets from both partners follow, and the male shows the female potential breeding grounds by standing in an "angelic position" with wings raised but not open and laying down the gift of prey. Without the handing over of such a food present, mating does not occur. When ready to mate, the female seeks physical contact and then assumes a bent mating position. The mating takes place in that the male stands on the back of the female and slides slightly to the side to allow cloaca contact , while supporting himself with his wings on the ground.
Brood
After the courtship, breeding begins in May. As a breeding ground, the snowy owl prefers areas with numerous rock ridges, protrusions and small hills. The female digs out a hollow on a raised, snow-free spot and lays 3–11 eggs , depending on the food available , every two days. After about a month, the young birds hatch again every two days, so that large age differences can occur within one brood. If there is not enough food for all the chicks, younger and smaller chicks will die first. While the female is incubating the eggs, the male provides it with food. After a further 6–7 weeks, the young birds have fledged.
The breeding success varies greatly from year to year. It mainly depends on the number of lemmings. With a high density of lemmings, a couple can manage with a territory size of two square kilometers. The short arctic summer leaves the newly independent young birds with little time to gain the necessary hunting experience. Therefore, the mortality among the young birds is very high.
Natural enemies
Aside from the skuas and arctic foxes that plunder unguarded nests, the snowy owls have few natural enemies.
Danger
In the past, numerous owls were shot down in their southern winter quarters in Canada. Today, however, illegal kills of snow owls rarely occur here. Due to truck traffic, there are relatively high accident losses, especially in Alaska and Canada, which, however, do not have a major impact on the overall population. In Scandinavia, there is a slightly decreasing trend in the population, which is likely to be related to global warming and to increasing disruption from human activities.
The International Union for Conservation of Nature ( IUCN) classifies the species in the Red List of Threatened Species as Vulnerable due to decreasing populations in North America . However, the population figures in Scandinavia and Russia and the entire population decline are considered uncertain. Should this be lower than the previously determined value, the snowy owl as endangered (will Endangered ) must be classified.
Others
- The snowy owl is the official bird of the Canadian province of Québec .
- She was also the mascot of the 2015 Canadian Women's World Cup .
- Hedwig , the owl from Harry Potter , is a snow owl. Hedwig in the books is a completely white female animal. In nature, only the males have white plumage, which is why they are portrayed in the films as a male owl. Hedwig is a fantasy bird.
- The O RLY established in net culture ? - Owl is a snow owl.
- Hugo von Blomberg dedicated a poem to a white owl: Deep in slumber Everything lies / Guarded only by the moon / A white owl flies / Silently through the night / Like an ancestor of death / She passed close by / It probably brings a slight shiver / But no horror.
supporting documents
Single receipts
- ↑ König et al., P. 317
- ↑ Snowy Owl - A Marine Species? (English) sciencedaily.com on December 24, 2008, accessed January 11, 2016
- ↑ Bubo scandiacus in the IUCN Red List of Threatened Species 2017.3. Posted by: BirdLife International, 2017. Retrieved December 10, 2017.
- ↑ The National Bird Project: Snowy Owl , on Canadiangeographic.ca, accessed February 14, 2019.
- ^ Hugo von Blomberg: Pictures and Romances . Eduard Trewendt Verlag, Breslau 1860, page 231
literature
- Claus König , Friedhelm Weick: Owls of the World . Christopher Helm, London 2008, ISBN 978-0-7136-6548-2
- Theodor Mebs , Wolfgang Scherzinger : The owls of Europe - biology, characteristics, stocks. Kosmos, Stuttgart 2000, ISBN 3-440-07069-7 .
- John A. Burton (ed.): Owls of the world - development - physique - way of life. Neumann-Neudamm, Melsungen 1986, ISBN 3-7888-0495-5 .
- Wolfgang Epple: The Owls - The mysterious birds of the night. Gräfe and Unzer, Munich 1994, ISBN 3-7742-1790-4 .
