Traveling thrush
| Traveling thrush | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
American thrush ( Turdus migratorius ) |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Turdus migratorius | ||||||||||||
| Linnaeus , 1766 |
The migrant thrush ( Turdus migratorius ) is a songbird species from the thrush family (Turdidae). It is widespread across almost the entire North American continent, in many places about as common and ubiquitous as the blackbird in Europe, and is also found a lot in settlement areas. It is therefore one of the best-known bird species in the United States and Canada and is there, although it is not closely related to the European robin , called American robin (= American robin) or red robin , or simply robin .
The diet of the American thrush is very varied. In the summer half of the year, soft invertebrates such as earthworms in particular predominate , in autumn and winter berries and other fruits make up the largest proportion. Some populations are resident birds , others migrate southwards or to lower altitudes in winter, where they often form large aggregations and sleeping communities.
description
The migrating thrush is the largest thrush in North America with a body length of 25 cm and weighs around 77 g. It is similar in body to the European blackbird.
In the breeding dress the male shows a dark gray to dark brown upper side with a blackish colored head, from which two white half rings above and below the eye clearly stand out. Sometimes there is also a piece of white eye stripe in front of the eye. The beak is yellow. The chin and throat are white and interspersed with fine, black dashes. The underside is predominantly lively dark orange to reddish brown, only the feathers on the lower abdomen, the under tail-coverts and the thigh fletching are whitish. The tips of the outer control feathers are white and form white "tail corners".
The female is generally weaker in color. The head in particular is less dark and can show hints of light streaked eyes and beard.
There is hardly any seasonal dimorphism, but the color of the freshly molted plumage appears a little more dull in autumn due to light fringes.
The juvenile plumage is similar to that of adult birds, but shows a black spot on the underside and a light spot on the upper side, including the wing covers. The head is lighter in color, with a pure white throat and diffuse, whitish-beige streaks of eyes and beard.
voice
The vocal repertoire of the American Thrush is similar to that of the Blackbird. The quality of the fluting Reviergesang (audio sample) is reminiscent of that of the mistletoe , but is less variable and more clearly structured. Compared to the blackbird or song thrush song, it seems quite monotonous and is much less loud. It consists of two- or three-syllable motifs that are quite similar to one another and are performed alternately at a constant, relatively calm tempo in stanzas 2–10 seconds long. It is aptly described in American as cheerily, cheer up, cheer up, cheerily, cheer up . There is also a soft chirping song.
The warning call (audio sample) is similar to the blackbird's "Tixen", but sounds a little more tinny or deeper and can be reminiscent of the call of a great spotted woodpecker. The screaming excitement call of the blackbird also has its counterpart (audio sample). Furthermore, a thin ssssp is described, which is released when it is blown .
distribution
The breeding area of the American thrush covers most of North America. The species is absent in the northern polar region. The distribution there extends to the extreme north of Alaska and the Yukon , to the middle of the Northwest Territories and Nunavuts , the north of Manitoba , Québec and Newfoundland . The species is absent in northwest Québec. Evidence from the summer half-year is available from Amchitka , the Pribilof Islands and from Herschel Island .
The American Robin breeds along the west coast on Kodiak Island , Haida Gwaii, and Vancouver Island . On the other hand, there are no deposits on the Farallon Islands and the California Channel Islands .
In California the area extends south to the White Mountains , the Panamint Range and the southwestern coastal plains around San Diego . In the Mojave Desert, the species only breeds scattered. It is also largely absent in southern New Mexico , central western and southeastern Texas , and along the coast of the Gulf of Mexico . In the Florida Panhandle and north of the peninsula Florida rarely it comes also in some regions but on the other peninsula.
In Mexico the distribution of the American thrush extends along the Sierra Madre Occidental , the Sierra Madre del Sur and the Sierra Madre Oriental and is there limited to altitudes between 1500 and 3500 m. There are two enclaves in Baja California Norte and in the Sierra Victoria in Baja California Sur .
Geographic variation
Between three and seven subspecies are recognized. In addition to the nominate form , which colonizes most of the northeastern half of the continent, the southwestern subspecies T. m propinquus has the largest distribution area. It is larger and more dull in color than the nominate form. In addition to the color and size variation from smaller birds in the east to larger ones in the west, there is a clinical (gradual) variation in the extent of the white tips on the outer tail feathers. This is largest in the east and smallest in the west. The remaining subspecies fall outside of this general scheme. T. m. nigrideus and caurinus , which are found in the cold and humid forests of Newfoundland and in the temperate rainforests on the west coast, are darker, smaller and longer-legged. Upper side darker than T. m. propinquus is the subspecies T. m. phillipsi in southern Mexico. The south-eastern subspecies acrusterus , on the other hand, stands out from the nominate form with its smaller body size and lighter, dull color. The isolated population of southern Baja California T. m. confinis is distinguished by a longer beak length, a beige-colored breast and a smoky gray top.
- T. m. migratorius Linnaeus , 1766 - Alaska (excluding the southeast) and Canada (excluding the southwest and east) south to northern South Carolina , northern Georgia , central and western Arkansas and eastern Texas, and west to Oaxaca , Arizona and Southern California
- T. m. achrusterus ( Batchelder , 1900) - southeastern United States, from West Virginia and Kentucky South
- T. m. nigrideus Aldrich & Nutt , 1939 - eastern Canada to Newfoundland
- T. m. Propinquus Ridgway , 1877 - southwestern Canada (southeastern British Columbia east to southwest Saskatchewan) and western USA (Montana to California and east to the Great Plains) and south to central Mexico (south to Jalisco, Oaxaca and Veracruz)
- T. m. caurinus ( Grinnell , 1909) - population of the temperate rainforests of the west coast: southeast Alaska southwards to Washington (including the Olympic Peninsula and Vancouver Island )
- T. m. phillipsi Bangs , 1915 - Jalisco , Guanajuato , southern Hidalgo and south to the south of Oaxaca
- T. m. confinis Baird , 1864 - isolated population in the mountains around Cabo San Lucas in Baja California
hikes
The traveling thrush is a partial puller . While the species is resident and barbed in Mexico , most populations in Canada and the northern US migrate regularly to the southern US and Mexico in the fall. Some birds hibernate further south on various Caribbean islands. In British Columbia, California and Newfoundland, however, the species partially overwinters in or close to the breeding areas and there are also individual overwinterers in other northern areas. In the event of cold spells and snowstorms in the wintering areas, there can be massive evasive movements.
After the breeding season, this year's birds gather in larger flocks, sometimes socialize with adult birds and form larger sleeping communities. In some cases, larger dispersal movements of young birds can also be felt from July . The autumn migration begins in August, but is not always uniform and directed south, but can be very different regionally. It usually becomes steadier in September, peaks in the eastern half of the US in October and ends in November, sometimes not until December. With regional differences, the homecoming extends over the months of February to April in the moderate latitudes. In more northerly regions, the first arrival dates can be much later, for example in Alaska around the end of April / beginning of May.
habitat
The American thrush originally occurs as an ecologically relatively unspecialized species in various open forest forms from the plain to the tree line as well as in subarctic willow bushes north of the tree line. In the north-west of the USA and in the south-west of Canada, for example, they can be found in floodplains and early succession stages on forest fire areas or in fields . In southwest Washington it prefers thinned stands within forests of Douglas fir and West American hemlock compared to old wood or clearcuts, and in the Appalachian Mountains it breeds at higher altitudes, where mountain meadows border on spruce and fir forests.
In addition, it can now be found everywhere in secondary forests, cultivated landscapes with trees and hedges, gardens, parks, farms, settlements and large cities. It breeds here preferentially in places where lawns or other short-grass areas alternate with trees and bushes and often reaches much higher population densities than in the primary habitats . Especially in the southern states of the USA, the species was able to record area gains between 1925 and 1940 due to increasing urbanization, woodland planting and irrigation. Before 1925, for example, in South Carolina and Georgia, deposits were limited to the hills and mountains in the north, and in Texas to the forested east. Today it also occurs there in the plains or the other parts of the country and there often exclusively in anthropogenic habitats.
nutrition
The Norway thrush feeds on invertebrates and fruits, with the focus of the food being very different depending on the season. Studies of stomach contents showed that in spring and summer the food is 90% animal, but from late summer to winter more than 90% vegetable.
The foraging for invertebrates takes place on the ground or in the bushes, where some of the prey can be read from the leaves. Like the blackbird, when hunting earthworms or insects, the traveling thrush often stares at a spot with its head tilted to one side and then stabs its beak from a twist. According to one study, success on lawns, measured in terms of frequency and number of attempts, depends on the length of the grass - foraging for food takes longer in higher grass. Larger flying insects are often hunted from behind. Fruits are picked up from the ground or picked directly from the bush. To do this, the bird usually sits in the branches and stretches its head towards the fruits that can be reached, but sometimes these are plucked from the shaking flight.
Reproduction
Norway thrushes are sexually mature from the first year. They have a monogamous seasonal marriage; however, due to the high degree of loyalty to the breeding site, there is often a long-term marriage. There are usually two annual broods, in the south often three. The breeding season is between April and June. Early broods were found from the end of March, and late broods into August.
Pair formation and the establishment of a territory take place one to two weeks after arrival in the breeding territory, but sometimes more quickly in the northern parts of the distribution area. In these populations, the pairs may find their way together on the train.
During the first broods of the year, the nest is often built in conifers or other evergreen shrubs, and more often in deciduous trees when the season is advanced. It is usually between 1.5 and 7 m high, rarely higher, lower or directly on the ground. It is erected in a fork of a branch or on a solid base such as strong branches or corresponding structures on human buildings. In the prairie or tundra, where there are no bushes, soil nests or nests on or on rocks are not uncommon. In the temperate rainforests on the west coast, a platform made of branches is often gathered as a base. Occasionally foreign nests are used, old ones repaired or built over.
The nest is built exclusively by the female; the male only helps with the transport of nesting material. The first nest of the breeding season usually takes 5–6 days to build, later nests are built within 2–3 days. The exterior is a compact bowl made of grass and stalks, small twigs, roots and moss. Sometimes feathers, paper, textile fibers or pieces are also used. Once the exterior is finished, it is lined with a layer of clay that can be up to 25 mm thick. The clay often comes from the ejections from earthworm holes. It is thrown into the nest in clumps and then spread by the female using movements of the entire body and feet. If there is no clay available, for example due to drought, this can interrupt nest building activities for a long time. After the layer of clay has dried, which can take one to two days, the nest is lined with an inner structure made of fine grass components. The outer diameter of the nest is on average about 120 mm, the height 65 mm. The trough is about 42 mm deep and 90 mm in diameter.
The female lays the eggs 1–5 days after completing the nest. In contrast to other passerine birds, their eggs are laid in the morning and not in the early morning. The clutch usually consists of four, less often three to six eggs. These are around 28 x 20 mm in size and are solid, dark greenish-blue. They also rarely show isolated points, spots or pale brown speckles. They are incubated by the female for 12 to 14 days.
As incubation usually begins with the first or second egg, the young hatch over several days. They are fed by both parents and fly out after 9-16 days. Then they are fed for about 10 days, in the case of second or third broods, the female is already busy building a new nest during this time.
literature
- Rex Sallabanks, Frances C. James (1999): American Robin (Turdus migratorius) in The Birds of North America Online (A. Poole, Ed.), Ithaca, Cornell Lab of Ornithology
- UN Glutz von Blotzheim, KM Bauer : Handbook of the birds of Central Europe (HBV). Volume 11 / II: Passeriformes. Part 2: Real Thrushes: Turdidae. AULA-Verlag, ISBN 3-923527-00-4 , pp. 1195-1208.
- DA Sibley: The Sibley Field Guide to Birds of Eastern North America , AA Knopf, New York 2003, ISBN 0-679-45120-X
- Peter Clement , Ren Hathaway: Thrushes. Helm, London 2000, ISBN 0-7136-3940-7 .
Individual evidence
- ↑ Andrew Spencer: XC13602 · · Robin Turdus migratorius . xeno-canto.org. May 24, 2007. Retrieved November 20, 2019.
- ↑ a b Glutz v. Blotzheim, p. 1199 (see literature)
- ↑ Manuel Grosselet: XC6242 migrating thrush Turdus migratorius . xeno-canto.org. June 11, 2006. Retrieved November 20, 2019.
- ↑ Andrew Spencer: XC14080 · · Robin Turdus migratorius . xeno-canto.org. June 19, 2007. Retrieved November 20, 2019.
- ↑ a b Sallabanks / James, section "Migration" (see literature)
- ↑ a b Gutz v. Blotzheim, p. 1199f, see literature
- ↑ a b c Glutz v. Blotzheim, p. 1202f (see literature)
- ↑ a b Sallabanks / James, section "Habitat" (see literature)
- ^ NT Wheelwright: The diet of American Robins: an analysis of US Biological Survey records . The Auk 103 (1986), pp. 710-725 ( PDF )
- ↑ LA zealot: Effects of grass length and mowing on foraging behavior of the American Robin (Turdus migratorius) . The Auk No. 97 (1980), pp. 576-580.
- ↑ a b c d e f Glutz v. Blotzheim, p. 1203f, see literature
- ↑ a b c d Sallabanks / James, section "Breeding" (see literature)
Web links
- Turdus migratorius in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2004. Retrieved on January 19 of 2009.
- Videos, photos and sound recordings on Turdus migratorius in the Internet Bird Collection
- Song of the migrant thrush ( WAV ; 298 kB)
- xeno-canto: sound recordings - American Robin ( Turdus migratorius )
- American bluebird feathers