Hawk owl
| Hawk owl | ||||||||||
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Hawk owl ( surnia ulula ) |
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| Scientific name | ||||||||||
| Surnia ulula | ||||||||||
| ( Linnaeus , 1758) |
The Sperbereule ( Surnia ulula ) is a medium sized owl , in the boreal coniferous forests Eurasian and North America is located.
Origin of name
It got its name because of its resemblance to the sparrowhawk ( Accipiter nisus ). Similar to the sparrowhawk, their underside is banded across. Also in the side profile and in flight it is reminiscent of a sparrowhawk. Like this, it has a fast and agile fighter flight and can reach its maximum flight speed very quickly after take-off. It is not only similar to the sparrowhawk in its plumage and flight pattern (with a rather long tail), but also in its way of life: it is active during the day and at dusk and hunts small birds and voles . The name Sperbereule was first used in German in 1773. Until about 1900 the names hawk owl, owl falcon and falcon owl were also used.
Appearance
The Sperbereule is provided with a body length of 36-41 centimeters, a medium-sized owl in the size of the Waldohreule like.
The tail of the hawk owl is remarkably long and wedge-shaped. The flattened head is small in relation to the body. Like many owls, she has a light face veil that is clearly framed in brown-black. The irises of the eyes are yellow. The beak is also colored light yellow.
The back plumage is brownish-black with white spots. On the underside, the plumage is white with narrow dark gray-brown transverse bands. This black and white banding continues to the tip of the tail. It also makes this owl easily recognizable in flight.
Male and female birds do not differ in their plumage; however, female birds are slightly heavier than males. Males weigh an average of 270 grams, female birds an average of 320 grams. Young birds are generally a little more gray-brown in color and do not yet have any clear banding on the underside.
voice
Like many owls, the hawk owl also has a number of very different sounds:
- The most common expression of both sexes, used in many sound variations and very unspecifically, is a short, loose trill, which accompanies almost every contact with conspecifics and every action - especially at mating time. Bubbling softly, purring, rumbling, hammering to rough-sawing, trills accompany the aggressive-looking pursuit flights for mating and defending against enemies, they also initiate the first handing over of prey and copulations. (Mebs & Scherzinger, p. 364)
The hawk owl sings to its conspecifics with its beak open, ruffles its plumage below the beak, bobs its tail excitedly or moves jerkily in the branches.
The male's territorial song can be heard most clearly, corresponding to a rolling or pearly "hu hu huhu ü ü üüüüüü" series of calls. The call begins relatively quietly and then increases in volume. If the two partners meet, these trills are a little shorter and are occasionally performed in a duet.
The begging calls of the females, which are reminiscent of a hoarse "chat", also belong to the courtship behavior. The boys' begging calls for food are more drawn out and hissier and are reminiscent of a "Tschschui-epp".
To the sounds of the enemy defense and in fighting between conspecifics include hissing and Schnabel miners .
distribution
The hawk owl inhabits the boreal coniferous forests of the Holarctic from northern Norway and Sweden to Kamchatka and Sakhalin as well as in Alaska and Canada . In 2013, for the first time since 1974, a pair was observed breeding in Estonia . The northern limit of distribution largely corresponds to the tree line.
Despite this extensive distribution area, only three subspecies are distinguished:
- Nukia ulula ulula lives in the north of the Palearctic .
- Nukia ulula tianschanica lives in the Central Asian Tianshan Mountains.
- Ora ulula caparoch differs from the two other subspecies in that it has darker plumage and is common in northern North America .
habitat
The hawk owl mainly uses the forest areas in which trees stand gaps and stand waiting areas in the form of dry trees are present. It is one of the species that benefit from logging in the Nordic forests. Sufficiently old trees must remain, however, which offer half-open tree hollows as a breeding opportunity and, in addition, enough raised hides are available for hunting. The hawk owl also lives in mixed forests if these are interspersed with enough open areas. For example, it can be found near raised bogs and dry hills, as well as near clearcuts.
The settlement density is mainly dependent on the density of their main prey, the voles . It adapts to the volume of voles, which varies from year to year, with sometimes very extensive migrations, but usually does not leave the boreal coniferous forests.
Hawk owls are so-called "survival migrants" - if the prey supply collapses, entire owl populations can emigrate from a region. In northern Europe, the snowy owl and the buzzard also show this behavior . Due to this migratory behavior, the hawk owl is counted among the vagile or nomadic bird species.
Prey animals
The food composition of the hawk owl fluctuates over the course of the year. During the time in which it is breeding and raising young, its prey consists almost exclusively of voles ( Myodes spec. And Microtus spec.). The hawk owl seldom preyed on animals heavier than 70 grams. It used to be believed that lemmings also play a larger role within the prey spectrum of hawk owls. Although the hawk owls are opportunistic hunters and adapt quickly to the volume of prey, lemmings are very rarely among the animals that are struck by the hawk owls.
Outside of the breeding season and the rearing of young, the percentage of voles in the total prey drops to 57%. Then the proportion that small birds make up increases significantly. Occasionally they also hit larger and heavier birds such as ptarmigan and hazel grouse, as well as thrushes. On average, birds then make up 30 percent of the prey. During this time, shrews made up a further significant proportion of the prey . If there is a lack of food, beetles and frogs are also captured.
behavior
Ways of hunting
The hawk owl hunts almost exclusively during the day and at dusk. Even bright full moon nights are not used by her for hunting.
The hunting methods of the hawk owl depend on the prey it wants to hunt. With the hide hunt, she spots mice on the ground, which she pushes down from this vantage point:
- ... to take off it leans its plumage slim, bends diagonally - partly horizontally - and looks highly concentrated ... To catch mice, the owl can fall almost vertically, it also glides flat on the ground or shakes the prey constantly . She grabs live mice with one or both legs, even when they are flying by. Only with larger prey does it land and adopt the "catching position" with its wings stretched far from its body. (Mebs & Scherzinger, p. 366)
Their distinctive flying skills are only really used when hunting birds. It is able to follow birds closely and to adapt to their flight maneuvers at lightning speed. Birds are their main prey during winter when mice are difficult to capture due to the high snow cover.
The prey is killed by walking with the catch and biting. The hawk owl often kills its prey with a targeted bite in the neck. If the hawk owl catches more prey than it needs in a day, it is deposited. They like to hide their prey in crevices and holes in tree trunks.
Resting behavior
Hawk owls behave very agile during the day and differ in this from most owl species. While turning their heads vigorously, they observe their surroundings from their waiting areas, bob their tails and frequently change their seat. These movements take place without introductory movements and are therefore very abrupt. This behavior makes her appear "hectic" to human observers.
In their typical resting behavior, hawk owls crouch upright with loosely fluffed plumage on the dry branches of exposed trees. They can be seen from afar - unlike other owl species, however, there is no so-called "hating" by other birds. Birds usually recognize the typical features of their predator "owl" - a squat shape, spherical head, eyes pointing forward - and react to this with alarm behavior and occasionally even attacks on the discovered owl. In the case of the hawk owl, on the other hand, this does not happen, since these appearance features are less pronounced.
Hawk owls like to bathe regularly and with great devotion. Completely soaked, they then climb into the branches with the help of their beak. Bathing in sand or dust has not yet been observed in hawk owls.
Reproduction
Courtship
Hawk owls usually live together in a monogamous seasonal marriage, that is, the couple only binds to each other for one breeding season. In rare cases, polygyny occurs in which a male provides prey to several breeding females.
Courtship activities can take place as early as autumn, but courtship mainly occurs in March and April. The courtship, especially at the beginning, is characterized alternately by aggressive behavior, mutual nibbling of the plumage, communal resting in the branches and common trill duets. The female in particular occasionally attacks the advertising male with her claws.
The male shows the female the breeding tree or the entrance to the breeding cave by flying there and luring the female with calls that resemble the later feeding calls. Mating is initiated when the male surrenders prey.
The nesting place
The hawk owl breeds mainly in tree hollows and prefers black woodpecker hollows . But it also breeds in abandoned bird of prey nests or - like the great gray owl - on decayed tree stumps.
The breed
Hawk owls only lay one clutch per year, but there are replacement clutches if the first clutch or the young brood is lost. Breeding begins as a rule in early April, the young usually hatch 28 to 30 days later.
Hawk owls are characterized by the fact that they adapt their clutch size to the food supply to a very high degree. Therefore, the clutch size in the hawk owl varies between three and thirteen eggs . The maximum clutch size is laid when your territory is characterized by a mass of vole. Since the laying interval between the individual eggs is one to two days and the female hawk owl begins to breed with the first eggs, the age range within a hawk owl brood can be very large. Clutches are usually five to eight eggs in size. Only the female breeds, the male provides them and later the nestlings with prey.
The boy owls
During the first three days after hatching, the only sparsely feathered nestlings usually lie flat in the nest before they are able to stand up for the first time. They can stand from the eighth to tenth day of life. The female initially divides the prey brought by the male and feeds it to the nestlings with enticing sounds. The nestlings can eat an undivided mouse from the 14th day of life, from the 16th day of life the young birds wear their chocolate-brown branch dress.
Young birds are at least 20 days old before they leave the breeding site. The point in time depends on the conditions at the breeding site and the age of the siblings:
- The age of emergence is up to 5 weeks for broods in safe tree hollows, but mostly only 3 to 4 weeks for open nests; however, in the hawk owl it can spread unusually broadly, which may have to do with the sometimes very high number of young. (Mebs & Scherzinger, p. 370)
At 30 to 32 days, the young birds can make their first short flights from one branch to the next. Until the autumn, the young birds are mainly provided with prey by the male; the female moults after the breeding phase. At the beginning of the autumn balz, the adult birds begin to drive the young birds out of the territory; however, the young birds' urge to migrate also begins. This youth migration is typical for all owls; in hawk owls, ringed birds have been found in the nest up to 1,800 kilometers from their breeding site.
Predators and enemy behavior
Hawk owls are endangered on the one hand by larger species of owls such as the eagle owl and by predatory mammals such as martens , which pose a particular threat to the still flightless hawk owls .
Hawk owls defend their brood very vigorously by flying attack flights on predatory mammals or people approaching the nest. Hawk owls also show a graded threatening behavior both towards potential enemies and towards conspecifics invading the breeding area, as they enlarge their body silhouette by changing the wing position. This threatening behavior is accompanied by a repertoire of loud, high-pitched alarm calls.
Life expectancy and stock situation
It is difficult for the hawk owl, which is not very faithful to its location, to determine data on the mortality rate of young birds, the average life expectancy and the general stock situation. The oldest ringed hawk owl that has been found was at least 8.4 years old.
The stock situation fluctuates greatly in the individual years. When voles are abundant, there are up to 4,000 breeding pairs in Finland . However, if the vole population collapses, there are sometimes only 100 pairs that brood there. For European Russia, the number of breeding pairs should be between 10,000 and 100,000. For Norway , Sweden and Finland, the population is estimated to be slightly more than 8,000 breeding pairs on average.
Hawk Owl in Germany
From 1790 to the winter of 2013/14, 171 records were made with 179 hawk owls in Germany. Of these 179 hawk owls, 102 were shot down between 1790 and 1929. More of the not so shy owls were caught. With eight references, there were most references in one year in winter 2013/14.
Others
Hawk owls are one of those owls that are occasionally kept in zoos . It is interesting for zoo keepers because, unlike most owl species, it already shows activities in the edge of the day. In the Cologne Zoo , a pair of hawk owls is kept together with long-eared owls in the so-called " owl monastery" .
literature
- Jürgen Nicolai : Birds of prey and owls. Compass nature guide. Gräfe and Unzer Verlag, Munich 1987, ISBN 3-7742-3805-7
- Theodor Mebs , Wolfgang Scherzinger : The owls of Europe - biology, characteristics, stocks. Kosmos Verlag, Stuttgart 2000, ISBN 3-440-07069-7 (The book by Mebs and Scherzinger comprehensively reproduces the way of life of the thirteen owls represented in Europe)
- John A. Burton (ed.): Owls of the world - development - physique - way of life. Neumann-Neudamm, Melsungen 1986, ISBN 3-7888-0495-5
- Wolfgang Epple: Owls - The mysterious birds of the night. Gräfe and Unzer, Munich 1994, ISBN 3-7742-1790-4 (simply written, suitable for children and young people)
Web links
- The hawk owl on owlpages.com
- The North American hawk owl subspeciesaghia ulula caparoch on owling.com
- Surnia ulula in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 31 of 2009.
- Videos, photos, and sound recordings of Umgebung in the Internet Bird Collection
- Photos at www.naturlichter.de
Individual evidence
- ↑ a b Wilhelm Breuer: Visit from the Taiga: The Spereule in Germany . National Park 4/2016, pp. 18–19
- ↑ Rarely seen hawk owl , on looduskalender.ee of November 24, 2013; Retrieved February 20, 2016.
