Hudson consecration
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Hudson consecration ( Circus hudsonius ) ♀ |
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| Circus hudsonius | ||||||||||||
| ( Linnaeus , 1766) |
The Hudson's consecration ( Circus hudsonius ) is a bird of prey from the hawk family (Accipitridae). It is native to the North American continent and is the only consecration of the Nearctic . Their breeding area extends from Alaska to California , their winter quarters range from the Great Plains to Colombia .
The Hudson's consecration can be found in open grass and river landscapes, where, in addition to small songbirds, it preyes on field mice ( Microtus ). Together with the very similar Eurasian Hen Harrier ( C. cyaneus ) it forms a super species .
features
Hudson harriers are medium-sized harriers and have the body structure typical of this genus, with a slim body and long wings. Like many other consecrations, they show a pronounced reverse gender dimorphism in terms of size ( Reversed Size Dimorphism , RSD) and both sexes also differ significantly in color.
anatomy
The female is around 9% larger and 45% heavier than the male. It weighs between 370–660 g (on average 515 g) and is 41–50 cm long. The wing length is 335–405 mm, which corresponds to a wingspan of about 97–122 cm. The tail of the females is 210-258 mm, their tarsometatarsus 80-89 mm long.
The male is significantly lighter and smaller with 280–470 g (mean 360 g) and 32–39 cm. The difference in wing length is somewhat less pronounced, it is 328–352 mm, which corresponds to a wingspan of 76–95 cm. The tail measures 193-238 mm in the male, the tarsometatarsus is 71-80 mm long.
plumage
The male's head, back and upper wings are gray in color. While the forehead and throat are usually a bit lighter, a darker asphalt gray dominates the back and upper wing cover. Only the tips of the five outer hand wings are black. A black end band runs along the lower edge of the wing, which widens towards the body. The white upper tail-coverts are mostly only visible in flight. The tail shows four or five dark bands on a gray background, the lowest of which is particularly broad and distinct. The underside of the male plumage from the chest down to the rear of the trousers (leg plumage) and tail covers is beige or whitish. Here, too, the wings are framed by the black ends of the hand wings and a dark end band. A few reddish pits are distributed over the trunk, under wing coverts and trousers. The underside of the tail, like the upper side, has dark, narrow bands, here on a white background. Legs, wax skin and eyes are yellow.
The plumage of the female forms a clear contrast to this: the head and the upper side including the wings and tail are greyish-dark brown in the basic tone. The head has white areas on the browbones, under the beak and on the cheeks. In addition, a wreath of bright feathers runs from the back of the head to the throat, which - unlike in the male - clearly distinguishes the veil from the rest of the plumage. White lines run down the neck, while sitting, white spots can also be seen on the middle wing covers. The outermost five hand wings have black tips; the dark banding of the hand wings is not always clearly visible, on the arm wings it is even less visible. An important identification feature in flight is the white rump , to which the broad gray-brown banded tail connects. The underside of the body of the female is white to cream-colored. Throat and chest are clearly dashed dark brown. On the flanks, trousers, under tail-coverts and under wing coverts the lines are less dense, more reddish and more irregular. The underside of the female arm wings is grayish, that of the hand wings is more beige. There is a dark banding over both of them, especially on the wings of the hand. The tail feathers are also broadly banded in black and white on the underside.
Juvenile birds show the same plumage pattern in males and females, which, as in many other species of the genus, closely resembles the plumage of the female. The differences lie in the darker upper side, which is more reddish than beige in color, and above all in the underside: The basic color is a rusty brown, which turns more and more yellow towards the legs and also becomes paler until spring. The dotted lines on the underside only go up to the chest and the banding of the hand wings is only weakly pronounced. The only clue to differentiate between the sexes is, besides height and weight, the color of the eyes. In juvenile males, the iris is initially light brown, grayish brown or greenish before turning yellow in spring. Annual females, on the other hand, initially show chocolate brown eyes, which become lighter over time.
Mauser
During the moult, adult Hudson harriers usually completely renew their plumage. In females, moulting usually starts before eggs are laid in spring, but can be postponed until the young are independent. The male moulting begins later, but is completed faster. In the second summer, juvenile birds change almost their entire dress and retain only part of the upper wing-coverts and the tail, less often a few arm-wings.
Flight image
The flight image of Hudson harriers is characterized above all by a rocking glide at a low altitude (about 3 m). The consecration keeps the wings in a V-position and only occasionally flaps with light, weak wing beats, while it covers long distances over meadows, cornfields or prairies. Occasionally it dives down into the vegetation to grab prey.
In the higher soaring flight the V-position of the wings is less pronounced or not recognizable, which is why the Hudson consecration is often reminiscent of buzzards ( Buteo ). However, it differs optically from these by the relatively long, slender wings and the narrower tail.
In addition, you can also observe other flight images: For example, wave-shaped ups and downs at great heights, which probably represent a territory behavior. Slow patrol flights with deep wing beats, in which the Hudson consecration lets the claws hang down, have the same purpose. For partner recruitment, flight maneuvers are used, in which above all the male falls from a great height like a falling leaf to the ground and then lands.
Vocalizations
Acoustically, Hudson harriers are inconspicuous birds. As a rule, they only call during the breeding season and when threatened, to warn the partner or to drive away the potential attacker. The warning call consists of a rapid, rattling staccato of kek-kek-kek-kek-kek calls. The courtship calls are uttered during the flight maneuvers that the male uses to woo females. The male calls with a high, ascending ouwiep while ascending and descending in the air. Brooding females, demanding food from their partner, emit a sharp, piercing wiiep that drops in pitch. When females return to their nestlings with food, you can hear a chuckling call.
distribution and habitat
The Hudson consecration is widespread across almost the entire North American continent. The breeding areas are almost exclusively in Canada and the USA and only to a small extent in the extreme north of the Mexican southern California . Birds are absent in eastern Alaska as well as along the north coast. In Canada , distribution gaps exist in eastern British Columbia north of Vancouver , but especially in the provinces of Newfoundland , Québec , Nunavut and the Northwest Territory , as large parts of these areas are in the polar climate zone . Basically, however, the Hudson consecration breeds with different densities in all Canadian provinces.
The Hudson consecration is widespread all year round in large parts of the northern USA, it is only absent as a breeding bird in the predominantly arid states of Arizona , New Mexico and Texas and in the southern states .
hikes
The winter quarters of the birds extend to Colombia and Venezuela and include the USA, Central America and the Caribbean islands . The time of departure for the wintering areas is between August and December and varies not only according to geographic region, but also according to gender and age. It is less the temperature than the availability of food that plays a role, because the majority of the songbirds hunted by the consecration migrate south themselves. The earliest break out are juvenile birds that migrate for the first time; Females only slightly later than males. This is followed by older females, the last group being adult males. The focus of winter quarters in the USA is on the river basins of the Great Plains and the Great Basin , which are also used by a large number of small birds for wintering.
Habitat
Reeds, cornfields, prairies and all kinds of open, flat landscapes with grass and shrub growth form the habitat of the Hudson Harrier. Especially during the breeding season it is dependent on wetlands. In the winter quarters it is mainly to be found on floodplains or in rice fields, where migratory birds are concentrated. It occurs from sea level up to 2800 m, but usually only breeds up to 1500 m.
behavior
Hunting and feeding
Field mice ( Microtus ) make up the majority of the prey . The Hudsonweihe is highly specialized in the hunting of these very small animals: Like the sympatric occurring short-eared owl ( Asio flammeus ), occupying the same ecological niche, it has a face veil that can be set up to locate to noise. Hudson harriers are able to locate field mice at a distance of 3–4 m with an accuracy of 2 °. Although it lacks the asymmetrical arrangement of the ear openings, as they have the owls, the acoustic locating ability of the consecration comes close to that of the barn owl ( Tyto alba ) and corresponds to that of the short-eared owl; there are only differences in the distance from the prey.
Hudson harriers usually hunt at low altitude over dense vegetation. They used the wind to cover long distances over a flat landscape in a short time. When the Hudson's consecration sees a prey below, it pushes down abruptly and grabs it with its claws.
Social behavior
The Hudson consecration is basically a solo walk. Outside of the breeding season, it usually lives alone and also sets off on its own to migrate south. Occasional exceptions are the colonies observed in other consecrations, in which several birds come together to roost. The number of birds can range from 20 to several hundred consecrations. Short-eared owls can also be found in these colonies, especially when the food supply is very large.
Courtship and mating
The male arrives in the breeding areas five to ten days before the female.
It shows numerous flight maneuvers that serve to attract couples and consist of several parts: First the male ascends in a circling manner and with strong wing flapping to great heights (30-40 m), then accelerates horizontally and finally in sinusoidal up and down movements through the To puff air. The birds drop to 3–5 m above the ground, but then shoot up again. At the peak of the upward movement, the Hudson consecration performs a half or full roll and utters a shout of ouwiep before falling again. In addition, the male also lets himself fall into a spiral path, while at the same time rotating around its own axis and, if it falls, it is reminiscent of a leaf sailing downwards. The Hudson's consecration accelerates this fall towards the ground, then often brakes abruptly and ends up on the potential nesting site.
Occasionally the female also takes part in these excursions or tries to woo males in this way or to drive rivals out of their territory.
Hudson consecrations often live in polygyny during the breeding season . The male mates with up to four females, which he then cares for all alone. The amount of time it takes to feed each female and the amount of food the male provides is not the same for all females. While the alpha female receives the most attention, subsequent females receive less food, depending on the order in which they mated.
Breeding and rearing of the nestlings
The start of the breeding season varies by around seven weeks, depending on the geographical latitude; it usually begins in April at the earliest and ends in September at the latest. The female builds a loose, round nest from grass, reeds and twigs, 30–80 cm in diameter, at a height of 5–60 cm near water or on damp ground. The clutch consists of one to seven, usually four to six eggs. They are incubated by the female for 29–31 days before the chicks hatch. The nestlings fledge after 29–42 days, but remain dependent on the care of their parents for several weeks.
Systematics and history of development
Originally, the Hudson Harrier was regarded as a subspecies of the Eurasian Hen Harrier, as the adult birds can hardly be distinguished from the outside and the two species are also very similar in behavior. However, since the differences in the genome are relatively large at 0.8–1.7%, they have been regarded as separate species for some time. Corn and Hudson consecration were separated from each other by the Bering Strait for about 410,000 years and have hardly changed externally, which can be explained by the lack of selection pressure in large parts of their distribution area. The only measurable difference lies in the longer wings of the American type, which are probably due to the further migration routes.
Together, the Hudson's Harrier and Hen Harrier form a super species . Both belong to so-called "steppe harriers", a line of development of the consecration, which mainly populates steppes and semi-arid grasslands. It is possible that the extinct forest harrier ( C. dossenus ) developed from the Hudson consecration. This very small consecration lived until the Polynesians arrived in Hawaii , but then died out due to introduced neozoa . The geographical proximity and occasional sightings of the Hudson consecration as an errant in Hawaii indicate a possible relationship .
The position of the Hudson consecration in the genus Circus is shown in the following family tree:
| Hawk species (Accipitridae) |
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The Hudson consecration is monotypical , that is, no subspecies are recognized.
Existence and endangerment
The population of the Hudson's consecration is estimated at 50,000 to 60,000 breeding pairs. The winter population in North America was estimated at around 110,000 birds in 1986. In the 1950s and 60s in particular, the use of organochlorine pesticides in agriculture led to a drop in populations, from which the population was only able to recover after the toxins were banned. Currently, the draining of swamps and moors and the intensification of agriculture are a threat to the habitat of the Hudson Harrier. In Canada, the Hudson Harrier is considered safe, in the United States a slight decline in the population is suspected. Because the Hudson consecration is rare in some US states, it is the subject of some local conservation programs.
Sources and References
literature
- William S. Clark, Brian K. Wheeler: A Field Guide to Hawks of North America. Houghton Mifflin Harcourt, 2001. ISBN 0395670675 , pp. 149-154.
- John Barnard Dunning: CRC handbook of avian body masses. CRC Press, 2008. ISBN 1420064444 , p. 53.
- John Andrew Eastman: Birds of Lake, Pond, and Marsh: Water and Wetland Birds of Eastern North America. Stackpole Books, 1999. ISBN 0811726819 , pp. 170-176.
- James Ferguson-Lees , David A. Christie: Raptors of the World. Houghton Mifflin Harcourt, 2001, ISBN 0618127623 , pp. 483-486.
- James Ferguson-Lees, David A. Christie: Birds of Prey of the World. Franckh-Kosmos Verlag, Stuttgart 2009. ISBN 9783440115091 , p. 142.
- Donald S. Heintzelman: Hawks and Owls of Eastern North America. Rutgers University Press, 2004. ISBN 0813533503 , pp. 64-67.
- William R. Rice: Acoustical Location of Prey by the Marsh Hawk: Adaption to Concealed Prey. In: The Auk 99, July 1982. pp. 403-413 (online as PDF ).
- Robert E. Simmons: Harriers of the World: Their Behavior and Ecology . Oxford University Press , 2000, ISBN 0198549644 .
- Noel FR Snyder, Helen Snyder: Raptors of North America: Natural History and Conservation. Voyageur Press, 2006. ISBN 0760325820S, pp. 81-85.
Web links
- Literature on the Hudson consecration in the Global Raptor Information Network
- Jill A. Dechant et al. a .: Effects of Management Practices on Grassland Birds: Northern Harrier. Northern Prairie Wildlife Research Center, 2002, doi : 10.3133 / pp1842L .
- Northern Harrier Circus hudsonius. The Peregrine Fund - Global Raptor Impact Network, September 13, 2009.
- Videos, photos and sound recordings of Circus Cyaneus in the Internet Bird Collection
- xeno-canto: sound recordings - Hen Harrier ( Circus cyaneus )
Individual evidence
- ^ A b John Barnard Dunning: CRC handbook of avian body masses. CRC Press, 2008. ISBN 1420064444 , p. 53.
- ↑ a b c d e f g h i j k l m n James Ferguson-Lees, David A. Christie: Raptors of the World . Houghton Mifflin Harcourt, 2001. ISBN 0618127623 , pp. 136-137, pp. 483-486.
- ^ A b c d e f William S. Clark, Brian K. Wheeler: A Field Guide to Hawks of North America. Houghton Mifflin Harcourt, 2001. ISBN 0395670675 , pp. 149-154.
- ↑ a b c d Simmons 2000, pp. 61-64.
- ↑ Noel FR Snyder, Helen Snyder: Raptors of North America: Natural History and Conservation. Voyageur Press, 2006. ISBN 0760325820S, pp. 81-85.
- ↑ Helmut C. Mueller et al. a .: Age and Sex Differences in the Timing of Fall Migration of Hawks and Falcons. In: The Wilson Bulletin 112 (2), June 2000. pp. 214-224.
- ↑ Terry Louise Root: Atlas of wintering North American birds: an analysis of Christmas bird count data. University of Chicago Press, 1988. ISBN 0226725405 , p. 53.
- ^ William R. Rice: Acoustical Location of Prey by the Marsh Hawk: Adaption to Concealed Prey. In: The Auk 99, July 1982. pp. 403-413.
- ↑ Simmons 2000, pp. 125-132.
- ↑ Wink & Sauer-Gürth 2000 , p. 182.
- ↑ a b Simmons 2000, pp. 24-32.
- ↑ Storrs L. Olson, Helen F. James: Descriptions of thirty-two new species of Birds from the Hawaiian Islands. In: Ornithological Monographs 45, June 1991. ISBN 0-935868-54-2 , p. 67.
- ^ Northern Harrier Circus hudsonius. www.globalraptors.org, September 13, 2009. Retrieved March 3, 2010.