Mud treaders
| Mud treaders | ||||||||
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Mud treaders ( Tringa semipalmata ) in plain dress |
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| Systematics | ||||||||
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| Scientific name | ||||||||
| Tringa semipalmata | ||||||||
| ( Gmelin , 1789) |
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The mud treadmill ( Tringa semipalmata ) is a species of bird from the family of snipe birds , the two subspecies of which differ significantly in their ecological demands. The western subspecies T. p. inornata breeds in inland swamps in the Prairie Pothole region and the Great Basin in interior Northwest America; the nominate form inhabits the east coast of North America from Newfoundland to Tamaulipas as well as the West Indies and breeds in salt marshes and brackish water swamps.
The Willet is in breeding plumage patterned inconspicuous gray-brown in plumage colored monochrome beige brown right, but stands out with a high-contrast, black and white wing pattern in flight. The Reviergesang (audio sample), which can be described as pill-will-willet , earned him his English name Willet . For a long time the species was placed in the monotypical genus Catoptrophorus . Investigations of the mitochondrial DNA revealed, however, that the mud treadmill belongs to the genus Tringa .
description
With a body length of 33 to 41 cm, the mud treadmill is the size of a common woodcock and the largest representative of its genus. The weight is between 200 and 330 g. The sexes do not differ in terms of plumage, but the female is slightly larger. The most striking feature of the species is the contrasting wing pattern in all clothes - a white band that runs in an arc over the arm wing and centrally over the otherwise black hand wing. It is accordingly also available on the lower wing. In addition, the under wing covers are almost completely black. The iris is dark brown. The color of the beak depends on age, season and subspecies and varies between black, black with a flesh-colored base to blue-gray with a black tip. Legs and feet are grayish. Webbeds are formed between the front toes, the one between the outer and middle toes being larger than that towards the inner toe.
Eastern mud treads ( T. s. Semipalmata ) in breeding dress
Eastern mud treaders in breeding dress, flying
Mud treads with a clearly visible wing pattern
Western mud treaders ( T. s. Inornata ) in breeding dress
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Adult dresses
Adult birds of the nominate form are finely dashed whitish-dark brown in the breeding plumage on the head, neck, neck and front chest. In front of the eye there is a light over-eye stripe , which continues indistinctly above and behind the eye. The chin and throat are a little brighter. Shoulder and back feathers are dark brown with gray-brown tips and indicated, marginal banding. The longest shoulder feathers are gray-brown with dark bands on the edge. While the middle of the abdomen below the breast and the coverts of the tail are white, the feathers on the flanks and lower breast are tinted yellowish-beige and have multiple V-shaped strings that merge into the finer dashed lines on the middle of the chest. The arm covers are mostly banded gray-brown or fine gray-brown. On the middle arm covers there is a dark banding that becomes coarser and wider towards the umbrella feathers. The large arm covers have an ever-widening, white border towards the hand wing and loosely scribbled feathers. The inner arm wings are completely white, the outer ones are blackish brown on the distal part, so that the white bases form a band that continues on the basal part of the otherwise black hand wings. The hand covers are dark brown to black. The rump feathers carry a dark, subterminal band on a lead-gray background . The upper tail coverts are white. The control springs are gray-brown on the distal part with blackish, scribbled banding, and white on the basal part.
The plain dress is much more uniform on the top, but interspersed with fine dark shafts. The head, neck, back and shoulder feathers are beige-gray, but the lower sides of the head and the front neck are clearly lightened. The area above the reins, the eye ring, chin and throat are light whitish. On the flanks and sides of the chest, the beige-brown of the upper side merges into the whitish lower side. The coverts under the tail are banded in doodle gray on a white background. The arm covers and umbrella feathers are beige-brown like the rest of the top. Otherwise the wing pattern corresponds to the brood dress. The rump plumage is lead gray. The upper tail-coverts are whitish in the basal part and then merge into the light gray of the central control feathers. On the outside of the tail, the control feathers become lighter to whitish.
Youth dresses
The youth dress is similar to the plain dress, but is generally more brown in the gray areas, whereby the dark shaft lines are partly missing. The rump is colored like the top and the upper tail-coverts are partly brownish. Back and shoulder feathers as well as the upper wing coverts are characterized by dark subterminal bands and beige end hems or are slightly banded. In the first simple dress, the wing feathers of the youth dress are still preserved and then appear quite worn.
distribution
The distribution area of the mud treadmill is divided into a western occurrence in the interior of Northwest America and one on the Atlantic coast and on the West Indies.
The western subarea extends over southeast Alberta , southern Saskatchewan and southwest Manitoba . In the United States, it encompasses large parts of Montana with the exception of the southeast and the Rocky Mountains to the west. In North and South Dakota and in the extreme north of Nebraska , the species occurs north and east and locally also west of the Missouri River . In Oregon it populates the southeast, in Idaho parts of the south and in Wyoming the west and the eastern center. In California it breeds in the extreme northeast, in Nevada locally in the north, in Utah in the Great Salt Lake region and in Colorado in two smaller occurrences in the north.
The eastern subspecies colonizes large parts of the Atlantic coast and the coast of the Gulf of Mexico . In Newfoundland , the mud tread is a rare breeding bird. It may breed on the Magdalen Islands . But it occurs on the coasts of New Brunswick , on the Prince Edward Islands and Nova Scotia . Furthermore, the breeding occurrences on the east coast of North America extend from southern Maine to northern Tamaulipas in Mexico. The species is also breeding birds in the Bahamas , the Greater Antilles , the Cayman and Virgin Islands , Antigua , St. Martin and Barbuda . It may also be found in Anguilla . The southernmost breeding area is found on Los Roques . In addition, there are numerous over-summerers in northern South America. A breeding occurrence in the Yucatán has not yet been confirmed.
hikes
The mud treadmill is a resident bird in the West Indies , the remaining populations are long- , medium- or short-range migrants , with the northern populations of Canada migrating the furthest. The breeding birds of the maritime provinces of eastern Canada cross large parts of the Atlantic to winter in northern South America. The western subspecies moves partly along the Pacific coast, but partly along the Mississippi River to the east coast.
The breeding areas are cleared as early as the end of July, and the last birds can still be found until September. The species arrives in the wintering areas between August and November. The spring migration takes place from March and is completed by the end of June at the latest. The main arrival dates in the breeding areas are between mid-April and mid-May, depending on the geographical location.
The main wintering areas on the Pacific coast - with the exception of occasional wintering further north - extend south from Humboldt Bay in California. Sometimes the species occurs there in inland waters such as the Salton Sea or in the San Joaquin Valley . On the east coast there are larger numbers of winterers from central Virginia southwards. The winter area then extends further over the coasts of Central and South America - on the west coast to central Chile and on the east coast to southern Brazil and Uruguay . This also includes the Galapagos Islands , Trinidad and Tobago and the islands off the coast of Venezuela .
The Mud Treaders was found to be a stray visitor in Hawaii and very rarely in Europe.
habitat
The two subspecies occur in similar habitat types, but differ significantly in their requirements in that the nominate form breeds almost only in habitats near the coast that are characterized by salt water.
The western mud treaders breed in the prairies of the Great Plains in moist grasslands or in swamps with short-grass, loose to sparse vegetation. Semi-arid areas near water bodies or with adjoining swamp areas are also accepted. The species is less common in cultivated land. Only temporarily existing wet grassland is preferred to permanent swampy terrain. At higher altitudes, the mud treadmill can also be found in salt marshes, salt plains or on wooded mountain lakes. However, semi-open or built-up areas are evidently avoided.
The eastern subspecies, whose distribution is limited to the Atlantic coast, predominantly populates salt marshes during the breeding season, but also offshore islands and beaches with silt-grass vegetation . It can also be found locally in coastal pasture or farmland. However, habitats dominated by freshwater are evidently mostly avoided.
During the spring migration, the western subspecies can usually be found in smaller inland swamps, and in autumn also on the banks of larger lakes. In the winter quarters, almost all coastal habitats from sandy beaches to rocky coasts to mangroves are visited.
nutrition
The mud treadmill feeds on insects , small crustaceans , molluscs, and poly bristles . Occasionally he also catches small fish. Among the insects, aquatic beetles dominate, the crustaceans small crabs, which can make up a large part of the diet in the eastern subspecies. The search for food takes place with the beak poking, probing or plowing in shallow water. Western mud treaders are mostly to be found on lake shores, in shallow swamps or floodplains, birds of the eastern subspecies in mussel beds, tidal pools or silt grass meadows.
Reproduction
Mud treaders lead a monogamous seasonal marriage. Due to the high loyalty to the breeding site and partner, long-term marriages are the rule in many places. However, it can also happen that partners meet again on arrival in the breeding area, but later breed with other partners.
Pair formation and courtship
Some of the mud treaders arrive already paired in the breeding areas and occupy territories, other pairs form in the group courtship, which is also joined by birds that have already been paired. The group mating is usually over three weeks after the arrival of the breeding birds, but can also occur again during the entire breeding season - especially if the number of eggs lost is high.
Courtship flights are probably only performed by unpaired birds. The male initiates courtship and flies off with wings held high and arms flapping. The female also flies up and stays in the air under the male, whose calls it joins in a duet. Then it follows the male in a slow descent to the ground.
Before copulation, the male approaches the female from behind with click-click calls, lowers the tail and increases the calling frequency. It lifts the wings over the back with a flutter, whereby the wing beats become faster. This form of courtship takes about 20-30 seconds. The gravid female lowers her head, crouching down, lifts the tail and calls clicking . The male jumps up with a flutter and grabs the female by the neck with its beak during the copula.
Nest building and clutch
Clutches are mainly found between the end of April and the end of June, most of them in the second half of May. In the maritime provinces of Canada, the main season is a little later between mid-May and mid-July. In South Carolina, after spring tides that wash away low-lying nests, there is often a second laying phase in which the affected pairs make replacement broods.
When choosing the nesting site, the male leads the female to a place with calls, forms a nest hollow in a bull with a beak or feet and a rotation of the chest and then stands up again. The female then repeats the turning movement with her breast and also sits down. This process can be repeated three or four times before a decision is made.
The nest is usually hidden in slightly higher grass. It is either formed in a tuft of grass or a bulten or consists of carried stalks. The nesting trough is about 16 cm wide and 5 cm deep. It is lined with finer plant material.
The clutch consists of four, slightly glossy, round to oval eggs, about 54 × 38 mm in size, with irregular brown spots on a beige to olive-beige background. They are placed at intervals of one to four days within 6 days. Additional clutches often have fewer eggs.
Brood and young rearing
The breeding period is about 25 days. Both parents breed, with the female usually sitting on the clutch during the day and only the male at night. The young are fleeing nests who are led by both parents and rowed over night . The female leaves the family after about two weeks, the male stays with the young for up to two weeks longer. Sometimes it separates from them when they fled, but it can stay with them for up to a week.
literature
- Peter E. Lowther, Hector D. Douglas III, Cheri L. Gratto-Trevor: Willet (Tringa semipalmata) in A. Poole (Ed.): The Birds of North America Online , Cornell Lab of Ornithology, Ithaca 2001, doi : 10.2173 /bna.579
- DA Sibley: The Sibley Field Guide to Birds of Eastern North America , AA Knopf, New York 2003, ISBN 0-679-45120-X , p. 149
Web links
- Tringa semipalmata inthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved November 23, 2013.
Individual evidence
- ↑ Andrew Spencer: XC13806 · · Willet Tringa semipalmata inornata . xeno-canto.org. June 14, 2007. Retrieved October 21, 2019.
- ↑ Richard C. Banks et al .: Forty-seventh Supplement to the American Ornithologists' Union Check-list of North American Birds , The Auk 123/3, pp. 926-936, 2006, PDF
- ↑ Lowther et al. (2001), section Distinguishing Characteristics , see literature
- ↑ a b c Lowther et al. (2001), section Appearance , see literature
- ↑ a b c d e Lowther et al. (2001), section Distribution , see literature
- ↑ a b Lowther et al. (2001), Migration section , see literature
- ↑ a b c d Lowther et al. (2001), Habitat section , see literature
- ↑ Lowther et al. (2001), section Food Habits , see literature
- ↑ a b c Lowther et al. (2001), Behavior section , see literature
- ↑ a b c d e f Lowther et al. (2001), section Breeding , see literature