Greater Buzzard
| Greater Buzzard | ||||||||||
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Buzzard ( Buteo lagopus ) |
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| Buteo lagopus | ||||||||||
| ( Pontoppidan , 1763) | ||||||||||
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The rough-legged buzzard ( Buteo lagopus ) is a representative of Real buzzards ( genus Buteo ) from the family of Accipitridae (Accipitridae). The northern species is represented almost in a circumpolar manner ; it is only absent in Greenland , Iceland and Svalbard .
Usually four subspecies are distinguished, which only differ slightly from one another. In general, the Eurasian birds become somewhat lighter in plumage towards the east and increase in size; the nearctic race B. l. sanctijohannis is the smallest and darkest.
Appearance
Nominate form ( Buteo lagopus lagopus )
Overall, the Greater Buzzard is somewhat larger and more long-winged than the Common Buzzard ( Buteo buteo ) and, compared to this, is much less variable in color. The top is more or less uniformly cinnamon brown in all clothes; a shade that is very rare in common buzzards. The tail is white in all clothes with a diffuse black end band only in juvenile plumage, but sharply set off in adult birds, over which there are some narrower dark bands in males. In contrast, the common buzzard occasionally shows a white tail, but then the rest of the upper side of the body is also very light. The strikingly round head and neck of the buzzard are light brown to light gray, in individual cases almost white. The top of the head and the area around the ears are usually a bit lighter. The darker shaft drawing of these body parts is differently clear, it can almost be missing. The beak is rather small. A dark, narrow band extends from the edge of the eye to the yellow base of the beak. The underside of the body is spotted in different shades of brown and gray, and elongated black stripes can also be interspersed. The belly is almost always black, the neck and chest area are noticeably lighter.
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The legs are feathered down to the toes, but this reliable feature is usually only recognizable from a short distance. The feathers on the legs are light gray to white with dark brown shaft markings. As with the common buzzard, the toes are colored yellow; the claws are black. The wing tips close with the tail of the sitting bird.
Seen from below, a flying buzzard looks very light, mostly gray-white with, in contrast to the common buzzard, a black wing bend and a black tail band. Buzzards fly with slow, deeply drawn wing beats and often sail. In comparison to the common buzzard, the buzzards shake much more frequently and skillfully and even in low winds. During the jolting flight, the buzzard constantly varies its flight altitude, this " yo-yo " flight often allows species to be identified at great distances. In gliding flight, the arm-wings are slightly raised, while the hand-wings are held straight or very slightly lowered. This creates a noticeable kink in the wing profile, a good distinguishing feature from gliding buzzards, which usually keep the arm and hand wings straight or lift in a V-shape when sailing. The frequent turning of the tail, which is somewhat reminiscent of a kite , is also striking and characteristic of the species .
The sexes do not show any pronounced reverse sex dimorphism , so that they are not always easy to distinguish. The females are slightly larger than the males and up to 20 percent heavier. Their plumage is slightly lighter than that of the males, especially in the head and chest area. The tail of the females usually ends with only one end band, while the males usually have two to three narrow bands in addition to a broad one.
Young birds are lighter than the adults, especially the black end band of the tail is not yet clearly pronounced.
B. l. menzbieri
This breed connects to the east of the distribution area of the nominate form . The very wide contact zone runs in the Ural region . Representatives of this subspecies are somewhat larger than those of the nominate form and usually also lighter. The underside of the body is drawn less high-contrast, the tail bands (especially the end band) are narrower than in the nominate form. The irises of these birds are yellow in contrast to the light brown of the nominate form.
B. l. Kamchatkensis
This subspecies inhabits the Kamchatka Peninsula and the northern part of the Kuril Islands . The birds are large, rather dark and drawn with little contrast. From large and dark representatives of the breed B. l. menzbieri they are very difficult to distinguish. They are significantly larger and brighter than the average representative of B. l. sanctijohannis . The two subspecies mix on the islands of the Bering Sea , while the contact zone with B. l. menzbieri is not exactly known.
B. l. sanctijohannis
B. l. sanctijohannis inhabits the subarctic and arctic areas of North America from Newfoundland westward to Alaska and the Aleutian Islands . The light specimens of this subspecies are somewhat smaller than those of the nominate form, but differ only insignificantly from it in terms of plumage. The dark specimens are uniformly brown on the top and gray-brown speckled on the underside. Even in flight , this breed is darker than the nominate form. In the view from below, the mostly uniformly dark coving feathers of the lower wing contrast clearly with the otherwise light wing. This breed can be confused with the Red-tailed Buzzard ( Buteo jamaicensis ) , especially in flight . The birds of the Canadian east coast are the smallest overall; in them the reverse sex dimorphism is greatest both in size and weight as well as in the plumage. To the west, the individuals grow larger, but the gender differences become smaller. Buzzards from western Alaska and the Bering Sea area show the greatest individual differences in plumage coloration.
Uniformly dark to melanistic specimens occur regularly only in North America and occasionally in Eastern Siberia. They were very rarely found in the rest of the distribution area.
measurements and weight
The size (measured from the tip of the beak to the tip of the tail) is between 53 and 63 centimeters, of which the tail accounts for about 22 centimeters. With a wing length of up to 48 centimeters, the wingspan of the largest birds can be over 1.5 meters.
The weight of a well-fed male averages around 1.2 kilograms, while females are up to 20 percent heavier.
voice
The buzzard is less vocal than the common buzzard, it is only relatively loud when the nest is disturbed. The main call is a loud, a little plaintive sounding, drawn out Pi-iii-äääh , which can be varied in its initial and ablaut. This call can be remotely reminiscent of the meowing of a house cat. It is performed mainly during mating flights. In addition, the species has a number of voice feeler, contact and alarm calls. The brooding female greets the male carrying the food with a short, not loud Viiääh , in threatening situations a short, sharp Pi-i-ää can be heard from both sexes .
habitat
The buzzard is a northern inhabitant of the mostly tree and shrub-free tundra . In Fennoscandia it inhabits the treeless mountain areas as well as loose birch stands in the subalpine zone. It breeds regularly, but in small numbers, in the tree tundra. In very good lemming years , the northernmost foothills of the taiga are also populated. Here its breeding grounds are mostly on the edge of the forest, preferably near water, or on the edge of very large clearings. The Greater Buzzard is generally an inhabitant of the lowlands; in Scandinavia and Alaska, however, it occasionally breeds at altitudes of up to 1400 meters. He likes to be near bodies of water, on the coast or along river valleys.
The winter habitats are more diverse, but his preference for open areas with good all-round visibility is also evident in the winter quarters. It is often found in coastal areas, marshland , in extensive grassland areas and moors , and in eastern and southeastern Europe and Asia also in steppes . In North America he often spends the winter on prairies .
distribution
Breeding areas
The Greater Buzzard breeds in a circumpolar manner in large areas of the Holarctic , close to and north of the Arctic Circle . In Europe, its breeding areas begin in southern Norway and extend in a relatively narrow strip across central and northern Sweden and the northern part of Finland along the Arctic coast to eastern Siberia, Kamchatka and the northern Kuril Islands. A narrow spreading finger runs along the coast of the Sea of Okhotsk to the south about 55 ° north latitude. The northern limit of distribution is formed by the Arctic coast; only a few islands near the coast have been settled. The southern limit of the brood distribution lies in the transition zone from the strauchtundra to the tree tundra. Only when there is a very good food supply and only temporarily does the species breed in areas south of it.
The breeding areas in the Nearctic begin in the east in Newfoundland , include the areas around Hudson Bay to the north and north-west , the southern part of Baffin Island near the mainland , the northern area of the Northwest Territories with most of the offshore islands, especially Victoria Island , and extend across northern and western Alaska to the Aleutian Islands .
The winter quarters lie south of the breeding areas and hardly overlap with them. Its northern limit is formed by the southern limit of the boreal coniferous forest belt . In Eurasia they are mainly between 58 ° and 45 ° north latitude, but in some regions, such as Southeast Europe, Central Asia and East Asia, extend significantly further south.
In Central Europe the Greater Buzzard can only be seen in the winter months; the total number of winterers fluctuates considerably from year to year. After its Nordic prey animals have increased in mass with simultaneously climatically favorable breeding conditions, particularly strong inflows have been recorded in Central Europe. Occasionally, individual birds over-summer in northern Germany, northern Poland and the Baltic States. In 1988 a successful brood was recorded for the first time in Lower Saxony .
Winter quarters in Europe
In Europe, the majority of the wintering areas are to the east of 10 ° East, but a not inconsiderable number also winters west to the Rhine and south to the Alps . The main European wintering areas are in southern Sweden, in the Baltic States , in Belarus , in the eastern half of Germany, in the Czech Republic , in Slovakia , in eastern Austria, in Hungary and in the Ukraine . In the case of particularly strong inflows, northeast Greece, Crimea and northwest regions of Turkey are also reached.
hikes
The buzzard is a distinct migratory bird in its entire range. Like all thermal birds, it is a day mover. Mostly he moves alone, less often in small groups. Concentrations of more than 100 individuals have been observed at certain particularly favorable resting places. Overall, its migratory behavior has not yet been very well researched in detail; little data from individuals with transmitters resulted in daily train routes of around 100 kilometers. The train distances are different. A bird ringed while nestling in northern Alaska on August 5, 1985 was found on October 10 of the same year in Montana , 3,300 kilometers from its place of birth.
Buteo lagopus clears its breeding areas from the end of August depending on the food supply and the height of the snow cover. The main route does not begin until the second decade of September and extends into October. With particularly favorable living conditions, individual individuals stay in their breeding areas until November.
Grouse buzzards mostly migrate southwards on a broad front , only south and central Scandinavian birds migrate westwards along the German North Sea coast and winter in south and west England. In some places these broad front streets lead into so-called draft funnels, where, especially in the autumn migration, many people can be seen pulling through. There is an accumulation of migratory Buzzards near Falsterbo , along the great Siberian rivers and in East Asia, albeit in significantly lower numbers, on the coast of the Chukchi Peninsula .
The peak migration numbers of the Nearctic birds are counted at the well-known observation points such as Hawk Ridge near Duluth , Minnesota , in the last decade of October. The main number overwinters in the northeastern states of the USA, where the species can also be observed in settlements and cities in winter. The area of the wintering areas extends over the North American plains westwards to northern Mexico.
The Greater Buzzard probably leads a nomadic life in its winter quarters and only stays longer in one place if there is a very good food supply. However, it is not known which distances the birds cover during the winter months.
The homecoming begins in March and reaches its peak in mid-April. The breeding areas are not reached before the end of April, but mostly not until May and in the extremely northern locations not until the beginning of June. It is often a few weeks after arrival in the breeding area before breeding activities begin.
Food and subsistence
Prey animals
The main food of the Greater Buzzard consists mainly of small mammals, especially voles of the genera Microtus and Clethrionomys, as well as various lemming species ( Lemmus sp. ). With sufficient availability, these animal groups make up between 60 and 90 percent of the total food volume. However, if voles are scarce, medium-sized birds, especially red grouse ( Lagopus lagopus ), can become the main prey. In winter and wherever these species have penetrated into its breeding areas, also in summer, the Greater Buzzard hunts partridges ( Perdix perdix ssp. ) And prairie chickens ( Tympanuchus sp. ). Small numbers of reptiles , amphibians and fish are captured. Insects (mainly crickets and grasshoppers ) and the carrion of animals of different sizes also play an albeit subordinate role in the diet of the species. The Greater Buzzard also prey on larger mammals such as mountain hares ( Lepus timidus ), polar hares ( L. arcticus ) and Alaska hares ( L. othus ) less often, but regularly .
Among the Microtus species, the earth vole ( Microtus agrestis ) and the Nordic vole ( M. oeconomus ) predominate , in the winter quarters the field vole ( M. arvalis ). Among the lemmings, species of the genus Lemmus are in the foreground, especially the mountain lemming ( L. lemmus ), the Siberian lemming ( L. sibiricus ) and in North America the brown lemming ( L. trimucronatus ). With a massed occurrence, bank voles , such as the northernmost polar bank vole ( Myodes rutilus ), and collar lemmings ( Dicrostonyx sp. ) Also become important prey animals.
If it is available, the winter food is the same as that of the summer; otherwise shrews and birds will be captured more often, and carrion will be taken in larger quantities.
Hunting methods
The hunting methods of the species are varied, but where it is possible, high seat hunting predominates. If a prey is spotted, it is usually followed by a short hunting flight close to the ground, the last phase of which is usually a gliding flight. The animals are always beaten on the ground and killed with their claws and sometimes with their beak. Successful hitting of prey in flight has very rarely been observed. If the prey cannot be surprised, it is only pursued for a very short time.
In favorable, especially windy weather conditions and in places where there are no places to sit, the buzzards hunt shaking at a height of around 20 to 50 meters. Similar to the kestrel ( Falco tinnunculus ), the shaking phases, which last around 10 seconds on average, are interrupted by short sliding joints. In addition, slow search flights somewhat reminiscent of consecrations and hunts over water like an osprey ( Pandion haliaetus ) are regularly observed.
behavior
Activity and territoriality
The buzzard is diurnal with a strong tendency to extend its phases of activity into the twilight hours. In its northern breeding areas it can be found actively for 24 hours (especially when there is a shortage of food), but it usually rests between 11 p.m. and 5 a.m. despite the brightness.
If a lack of prey does not force them to remain active, the Buzzards also take long rest periods during the day. The posture is usually a little more horizontal than that of a resting buzzard.
Territories of different sizes are occupied in the breeding area, depending on the food supply, but only the wider area around the nest is defended. In bad feeding years, territorial behavior does not occur. Buzzards are very well tolerated by other species; their nests are often in the immediate vicinity of the nest of a peregrine falcon ( Falco peregrinus ), gyrfalcon ( Falco rusticolus ) or common raven ( Corvus corax ).
There is still no in-depth knowledge of the territoriality of winter quarters. If there was a good food supply, groups of up to 40 individuals were counted in a comparatively small area, and the presence of food competitors is usually tolerated.
Enemy behavior
In the breeding grounds, the rest of the nest area is vigorously defended against conspecifics and predators. While there are seldom physical arguments between conspecifics, potential nest predators are attacked directly. Skuas ( Stercorarius sp. ) And snowy owls ( Bubo scandiacus ) in particular, as well as larger land predators such as arctic foxes ( Alopex lagopus ), wolves ( Canis lupus ) and wolverines ( Gulo gulo ) are attacked directly from a great distance from the nest and are often successfully driven away.
Breeding biology
There is no reliable information about the time of sexual maturity; in particular, it is unknown whether - as with the common buzzard - yearlings can already brood. However, buzzards probably do not start breeding until they are two years old, and some do not even breed until they are three.
Sexual activity depends on the food supply in the breeding areas. The pair bond is only intensified when there is good to very good availability of food animals, and nests are built, eggs laid and brood. Depending on the degree of deficiency, there is a very differentiated reaction to poor food conditions; in extreme cases, courtship and nest-building activities are completely omitted or there is migration to better-supplied areas. Remaining Buzzards sit on only small clutches, which are often given up during the breeding period.
Pair formation and pair bonding
For some of the buzzards, pairing begins in late winter; these return to the breeding areas already loosely paired. Others only begin there with the courtship. They show impressive flights with widely spread wings and spread tails, accompanied by characteristic calls. The male also performs various flight capers.
Mated buzzards lead a monogamous breeding season marriage. However, there are indications that, at least for some, the bond does not expire in the winter months and can even last for several years.
Nest location and nest
According to the different habitats that the buzzards inhabit, the nest locations are also diverse. Wherever it has the opportunity, the species prefers to nest on ledges, small rock islands, on flat spots on embankments or along deeply cut river valleys, along the coast also on cliffs. In the tree tundra he builds tree nests, usually in the topmost tree section. The rarity of these nesting opportunities in its habitat, however, often forces it to build ground nests in completely open tundra. Most of the ground nests are in dry, slightly elevated areas that allow a good all-round view.
The nest itself is quite a voluminous structure, consisting of twigs and twigs, well padded with grass, various mosses, animal hair and feathers. This insulation is particularly thick with ground nests. Newly created nests have a diameter of about 80 centimeters, but with prolonged use they grow into voluminous structures of up to 150 centimeters in diameter. The nesting material is brought in by the male alone and built in by both birds. Nest building continues even during the breeding season. Sometimes existing nests of other Nordic birds of prey are also used.
Clutch and eggs
Whether a clutch is formed at all and the size of the clutch itself is influenced by the food supply, but the exact relationships are still the subject of scientific research. In any case, the clutch sizes can vary considerably from year to year. A normal clutch contains three to four eggs, but sometimes only one egg is laid. The laying interval for normal lay is 24 hours, only the last eggs of larger clutches are laid at a longer interval. In years of mass reproductions of prey, clutches of up to seven eggs were found. Additional clutches occur when the first clutch is lost and rarely contain more than two eggs.
The basic color of freshly laid eggs is greenish to bluish and later changes to a dirty white. They are abundantly covered with reddish brown and purple spots. The average dimensions are 57 × 45 millimeters.
Brood
The eggs are almost exclusively incubated by the female, who is supplied with food by the male during this time. The incubation period is 31 to 37 days, depending on the weather. The female incubates from the first egg, so that the development stage of the chicks is very different with a laying interval of one day or more. Breeding does not begin before mid-May.
At first the male alone provides the food for the female and the young; the female divides the prey and feeds it. Later both parents hunt and feed.
In the first few days, the downy pups are largely inactive except for feeding. They get their first feathers when they are twelve days old. At around four weeks they can cut up the prey themselves and stand upright in the nest. The first attempts at flight begin at the age of a little over 30 days, but very few young birds are fully fledged before their 40th day of life, the males apparently a little earlier than the females. The boys are then largely dependent on their parents for three to four weeks before they migrate . In late broods, the lead time leads directly to the autumn migration.
Life expectancy
There is little data available on life expectancy. 48 recoveries of the breed B. l evaluated in the 1990s by the Cornell Lab of Ornithology . sanctijohannis showed an average life expectancy of just over 21 months. However, due to the small sample size, this information is not representative. The oldest Buzzard found so far in the wild was a little over 18 years old.
Inventory development
There are only very rough population estimates, the maximum estimate is 500,000 breeding pairs worldwide. The species shows a strongly fluctuating population development; however, longer lasting declines are not found. Therefore the species is listed according to IUCN with LC = least concern .
In Europe, the number of breeding pairs is estimated at around 75,000 pairs; the stocks have remained stable in recent years, with a slight decrease only in Sweden. That is why the European portfolio is rated S = secure .
Name derivation
The word part “rough” in the species name has become somewhat incomprehensible, it no longer has anything to do with the current meaning of the adjective “rough”, which originally meant “hairy”, “feathered”, furry. In the fairy tale Allerleirauh , the girl wears a robe made of various types of fur. Remnants of the original meaning have only been preserved in the expression Rauchwerk for fur goods and in the hunting phrase rough for moult . In ornithology, this term is still used for species whose legs are feathered down to the toes: barn owl , grouse .
The scientific generic name buteo designates a bird of prey for Pliny, probably the common buzzard. Lagopus is made up of the Greek λαγῶς lagōs "hare" and πούς pus "foot", ie "hare foot", and also alludes to the feet, which are feathered to the toes.
Others
Some Central European countries use the species as a former breeding bird; Today, however, it is generally assumed that the species has not bred in Central Europe in the last few centuries, so that this information is most likely based on incorrect determinations.
literature
- Marc J. Bechard, Theodore R. Swem: Rough-legged Hawk (Buteo lagopus). In: The Birds of North America. Edited by Alan F. Poole , Peter Stettenheim and Frank B. Gill . The Birds of North America Inc. Philadelphia PA. American Ornithologists' Union, Washington 2002, No. 641. ISSN 1061-5466
- James Ferguson-Lees , David. A. Christie: Raptors of the World. Helm Verlag, London 2001, pp. 704-710. ISBN 0-7136-8026-1
- Urs N. Glutz von Blotzheim (Hrsg.): Handbook of the birds of Central Europe . Volume 4: Falconiformes. Edit and a. by Kurt M. Bauer and Urs N. Glutz von Blotzheim. Aula, Wiesbaden 1989 (2nd edition), ISBN 3-89104-460-7 , pp. 535-557.
- Hans-Günther Bauer, Peter Berthold : The breeding birds of Central Europe. Existence and endangerment. Aula, Wiesbaden 1997, ISBN 3-89104-613-8 , p. 504.
- Theodor Mebs : Birds of prey in Europe. Biology, population conditions, endangerment. Kosmos nature guide. Franckh, Stuttgart 1989, pp. 87 ff. ISBN 3-440-05990-1
- Benny Génsbol, Walther Thiede: Birds of prey - All European species, identifiers, flight images, biology, distribution, endangerment, population development. BLV, Munich 1997. ISBN 3-405-14386-1
- Viktor Wember: The names of the birds of Europe. Meaning of the German and the scientific names. Aula, Wiebelsheim 2005. ISBN 3-89104-678-2
- Franz Müller, DG Müller (Hrsg.): Wildlife information for the hunter. Vol. 2. Game birds. Kessel, Remagen 2006. ISBN 3-935638-60-4 (summary of earlier publications from "Jagd + Hege")
- Theodor Mebs, Daniel Schmidt: The birds of prey in Europe, North Africa and the Middle East - biology, characteristics, stocks. Kosmos, Stuttgart 2006. ISBN 3-440-09585-1
Web links
- Birdlife international factsheet
- The Greater Buzzard on Greifvogel.com
- Birdlife Europe factsheet (PDF file; 250 kB)
- Buteo lagopus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 31 of 2009.
- Feathers of the Greater Buzzard
Individual evidence
- ↑ Voice example ( Memento from September 29, 2007 in the Internet Archive )
