Hut singer
| Hut singer | ||||||||||||
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Bluethroat warbler ( Sialia mexicana ) |
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| Sialia | ||||||||||||
| Swainson , 1827 |
The hut warbler ( Sialia ) form a genus of passerine birds comprising only three species within the family of thrushes (Turdidae). All three species, the red-throated hut warbler , the blue-throated hut warbler and the mountain hut warbler inhabit North America ; the distribution area of the Rotkehl-Hüttensänger extends to Central America .
The birds, which are just about the size of a song thrush but are significantly lighter, have an intense blue color, especially on their backs, which is what the English name Bluebird refers to. In their shape they are more like flycatchers than thrushes. They are cave-breeders and feed mainly on insects, in autumn and winter also on berries and fruits. The northern populations of all three species are migratory birds. Hut singers are among the most famous songbirds in Canada and the USA. Like all smaller cave breeders in many regions of the Nearctic , the hut warriors suffer from cave competition from the introduced and rapidly spreading European star , to which they are usually subject in direct disputes. However, through intensive use of special nesting boxes, it was possible to largely compensate for the decline in populations in many regions. None of the three species is currently on an IUCN list of hazards .
Appearance
Cottage warriors are slender, large- and round-headed birds. The neck area is hardly separated from the trunk. Their most distinctive coloring features are the blue head and back and the equally colored tops of the wings and tail. The underside coloring is different for the three types. Male red-throated and blue-throated warblers are deep cobalt blue all over the top, wings, and tail. The throat of the red-throated hut warbler is rust-red, of the blue-throated hut warbler blue or blue-gray. The breast of both species is reddish-brown, the belly of the red-throated warbler is whitish, and of the blue-throated warbler, it changes from blue towards the rump into gray. The mountain hut warbler is light sky blue throughout; the blue is more intense on the back and wings. The eyes of the hut warbler are dark, large and round; a whitish eye ring can be seen especially in the females and young birds. The beak is horn-colored to black, relatively short and pointed.
The size of the hut warbler fluctuates between 16 and 22 centimeters, their weight between 26 and 32 grams, whereby the females are on average slightly heavier with the same size. Hut singers are therefore only half as heavy as the song thrush, with a comparable maximum size. The red-throated hut warbler is the largest and heaviest species. The blue-throated and mountain hut warbler are slightly smaller. All three species are relatively long-winged. The mountain hut warbler has the longest wings, with the folded wings almost ending with the tail end; In contrast to the other two species, this one is also rather long-legged.
All species are easy to distinguish, only hybrids, which occur occasionally between the blue-throated warbler and the mountain hut warbler, are more difficult to identify. The size and weight dimorphism is marginal , while the color dimorphism is conspicuous. Females have the same color elements as males, but they are significantly paler, more washed-out in color. In the head area, gray tones predominate, the blue is mostly limited to the caudal back, the upper side of the wings and the upper side of the tail. Identifying young birds is just as easy as differentiating between the sexes, although it is a bit more time-consuming to assign them to sex. Young birds of all three species have conspicuously white dotted or dashed plumage on a maroon ground in the upper back and shoulder area.
voice
The vocal repertoire of blue-throated and mountain hut singers is comparatively simple; they mainly have calls that sound like kje , which are uttered individually and sharply or in long series of calls. In addition, soft chirping sounds can be heard. The chants and calls of the Rotkehl hut singer are significantly more diverse. His singing is rich and varied. The timbre is somewhat reminiscent of that of the native blackbird , but is shorter and less melodious. Quiet chattering calls and hard chuck alarm calls can also be heard. In aggressive situations, all three species of Schnabelknappen can be heard.
distribution and habitat
The distribution of the hut warbler is limited to North America and the northern and central parts of Central America.
The red-throated hut warbler, which is widespread from southern Canada to the Gulf coast and from the Atlantic to the Great Plains , along the rivers to the eastern foothills of the Rocky Mountains , has the largest distribution area . In addition, it populates large areas in central Mexico. Its occurrences reach into central Nicaragua , split up like islands .
The breeding area of the mountain hut singer is also very large. It extends from the Yukon in northern Alaska over the Rocky Mountains south to the southwest USA and northernmost Mexico.
The distribution area of the blue-throated hut singer is somewhat smaller and more fragmented. It consists of two larger, contiguous areas and a few small islands in between. The northern area begins in British Columbia and runs south along the Pacific coast to northern Baja California . The larger southern and central American distribution part extends south from the central USA to the volcanic belt of central Mexico.
The wintering areas of the red-throated and blue-throated warbler are in the southern breeding areas of the two species, in the case of the mountain warbler they extend far into southern Mexico.
Habitats
Hut singers are residents of open, loosely tree-lined landscapes. They colonize light pine forests , forests after fires and storm events, light oak-pine mixed forests and pine- juniper stands, the mountain hut warbler also alpine meadows and loosely tree-lined tundra . They can inhabit wetlands as well as dry savannas and semi-deserts . Areas with too dense trees and dense vegetation are avoided as well as intensively used agricultural land. They are also found on farmland, particularly pastures, in large orchards, parks and cemeteries, and along roads and railroad lines, where they can find nesting opportunities in telegraph poles. By placing numerous nest boxes, they were also able to penetrate the green areas of large cities and larger house gardens.
The red-throated hut warbler and the blue-throated hut warbler are residents of the lowlands as well as of heights of up to 2400 and 2900 meters respectively. The highest settlement densities of the blue-throated hut warbler are in the submontane and montane zone between 1500 and 2400 meters.The mountain hut warbler occurs in the north of its range at low altitudes and near sea level, but also inhabits areas in the central Rocky Mountains at heights above 3000 meters. The highest nesting sites were found at almost 4,000 meters above sea level.
The winter habitats are very similar to the breeding habitats, but are usually more open than these. Hut warblers often overwinter in semi-deserts with only sagebrush and other dry bushes.
The sizes of the breeding territories vary between a few thousand square meters and a few hectares. In the mountain hut singer they seem to be the largest on average. The territories are around the breeding cave; above all this is intensively defended against cave competitors. The defense of food territories differs regionally and individually; it seems to be the least developed in nest box brooders of the red-throat warbler, they show almost colony-like breeding with a conspicuous preference for nest boxes in close proximity (10–40 meters) to other nest boxes occupied by conspecifics. In the other two species, the smallest distances between occupied breeding caves are around 100 meters. In winter, in addition to individual territories, group territories are established and defended, which usually consist of a pair of parents and their offspring and other adult birds that apparently had no reproductive success.
hikes
None of the three species is an obligatory migratory bird , but many of the birds that breed in the north of their range leave their breeding area outside of the breeding season. Most of the hut warriors of the southern USA, Mexico and Central America are resident birds , or birds that undertake very small-scale, especially vertical migrations. In urban areas, mainly in southeastern Canada and the northeastern USA, many red-throated warblers overwinter due to the intensive winter feedings and the more favorable urban temperatures. The tendency towards long migration distances is least pronounced in the blue-throated hut warbler. It mainly moves vertically into lower-lying areas, or if there is a lack of food or very poor climatic conditions, it seeks relatively small-scale, more favorable regions. The Rotkehl-Hüttensänger is also mostly a resident bird or a partial migrant. Only the northernmost populations largely clear their breeding area and move southward. Their train distances are around 2000 kilometers, but in exceptional cases also significantly longer. Occasionally, red-throated hut warriors reach the Bahamas and Cuba .
Of the three species, the mountain hut warbler shows the greatest willingness to migrate. The birds of Alaska, Canada and the northern USA are largely obligatory long- distance migrants, whose migration distances are sometimes over 6000 kilometers.
Hut singers pull mostly at night. Train groups of several hundred individuals occur, but are rare. Cottage warriors usually migrate in small groups of less than 30 birds.
Contact zones
Although there are extensive contact zones between the species, mixed broods are very rare. Only one mixed breed in captivity was known between the red-throated and the blue-throated slug. The mountain hut warbler hybridizes in the contact areas with both the red-throated hut warbler and the blue-throated hut warbler. Hybrids of these species also breed fertile with true- breeding individuals and other hybrids. A large study of over 8000 breeding pairs in the Canadian province of Manitoba , where the breeding areas of S. sialis and S. currucoides overlap, revealed a proportion of visually clearly identifiable mixed broods of just over half a percent. The hybrids have the plumage characteristics of both parents, the song of hybrids between S. sialis and S. cucurrcoides is more similar to that of the red-throated slinger .
Food and subsistence
Hut singers are omnivorous . The proportions of animal and vegetable food vary from species to species and vary according to the season. Overall, more animal food is consumed by all species in the course of the year; in the pre-breeding season and the breeding season, the huts warbler are almost exclusively carnivorous . The mountain hut warbler is largely dependent on animal food throughout the year; with him the share of vegetables is on average below 10%, with the other two species around 30%.
Hut singers are opportunistic food generalists . The largest parts of their food spectrum are those prey or berries that are available in abundance and are easy to obtain.
In all three species, the animal diet consists mainly of insects, with preference given to larger species. Beetles , caterpillars , crickets , grasshoppers , dragonflies and hymenoptera are among the main prey animals. To a lesser extent, spiders , worms and snails become the food of the warblers. At least occasional prey also includes the American pygmy shrew and other very small species of the genus Sorex , as well as very small lizards and tree-dwelling frogs .
Four fifths of the vegetable diet is consumed in autumn and winter. This includes all berries and fruits that ripen in the distribution area, in particular blackberries , raspberries , elderberries , juniper berries and many others, but also seeds, such as those of the knotweed and various sumac plants, especially from the genus Rhus , or the berries of mistletoe , from their availability Winter populations can be largely dependent.
The three species do not differ significantly in their methods of prey acquisition. All three prefer to hunt insects and other prey from a raised hide, 0.5 to 5 meters above the ground. From there, hut warblers can spot their prey at distances of up to 40 meters, depending on the type of vegetation. The prey is beaten on the ground and either eaten there or taken to a feeding place. Beetles are hit against a hard surface several times before they are swallowed. Other hunting methods are bottom hunt, with huts chasing prey with both legs hopping, flight hunts both by means of short excursions from a hide and continuously, especially when there is a large range of swarming insects, as well as short, ground-level shaking over a potential prey. The latter, very energy-intensive hunting method is most frequently and persistently used by the mountain hut singer. More rarely, hut warriors also search leaves and twigs for small insects, which they pick up from there. Hutwingers pick fruits and berries directly from the branches or collect those that have fallen from the ground. All three species visit feeding stations.
behavior
Locomotion - comfort and rest behavior
Hut singers are diurnal. The flight is low, with rather slow, irregular wing beats, they only cover longer distances at higher altitudes. On the ground they move hopping, often hopping sideways and only moving over short distances. Cottage warriors can climb up trunks, and young birds that have not yet fledged have this ability. They sit in an upright posture at the hunt. Outside of the breeding season and when there is enough food available, hut warriors spend almost two thirds of their time resting or caring for their plumage, sunbathing or water bathing. Outside the breeding season, small groups rest together in sheltered dwellings, in cold weather also in larger tree hollows or other caves and niches. Occasionally, sleeping groups also gather in the inner area of extensive mistletoe. During the breeding and early nestling period, the female sleeps in the nest, the male in its vicinity.
Agonistic and social behavior
In the pre-breeding and breeding season, all types of the warbler are territorial and extremely aggressive towards conspecifics and a large number of birds, as well as towards some mammals and reptiles. The intraspecific aggression is primarily directed against the sexual partner. Intersex aggression is less common. Hut singers defend territory of varying sizes, which includes the cave site and the surrounding area. The core zone in particular is intensively defended, while confrontations with neighbors in the peripheral areas, which often overlap with other territories, are less frequent and less violent. Internal disputes can lead to intense contact fights, which can also result in injuries. The adversaries can completely forget their surroundings and thus easily become victims of predators themselves.
Potential cave competitors such as different types of titmouse , woodpeckers , swallows , wrens , nuthatches , owls , the introduced European star and the house sparrow , which is also a neozoon in the Nearctic , try to drive hut warriors from the breeding area. Red-throated warblers destroy the nests of the house wren and various species of titmouse. The females are particularly active in defending the breeding ground. Huts warns of predators such as various species of martens , raccoons , house cats, birds of prey and tree-climbing snakes, usually from safe cover. People who come too close to the breeding cave are sometimes attacked directly. Outside of the breeding season, migratory groups defend their feeding grounds, for example some mistletoe-bearing trees, the resident birds remain territorial even in winter, but the defensive readiness and the aggressiveness of the actions are significantly milder.
Outside the breeding season, hut warriors live in family groups or in roving food-seeking groups of usually no more than 30 birds. Within the groups, the individual birds keep a distance of about one meter. They are in voice contact with one another; other social interactions were not observed. Hut singers only rest close together when the weather is bad.
Breeding biology
Phenology
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The earliest broods of the blue-throated hut warbler were recorded in its most south-westerly breeding areas in mid-February, those of the red throated hut warbler towards the end of the same month. Most of the first broods of both species do not begin until the end of March, however, the main breeding season begins in the second decade of April and lasts until mid-May. The mountain hut warbler breeds later, under very favorable conditions as early as the end of April, but usually not until May and in the northern and very high areas in June.
Pair formation
Hut singers reach sexual maturity at the end of their first year of life and usually breed at this age as well. They have a monogamous seasonal marriage; Reparations and long-term partnerships are common. A Californian long-term study found for the blue-throated hut warbler that only 7 out of 117 pairs changed partners within 12 years when they returned to the breeding site. A forced change of partner during the year was only observed in three cases in the same study. Nonetheless, out-of-pair copulation is likely to occur very frequently in all three species: at least one fifth of the boys do not have their mother's partner as their father. The frequency of out-of-pair copulations is greatest in first-breeders. Various other partnership systems occur in all three types, but are rare. Polygyny was observed most frequently ; usually two females of a male occupy neighboring but different territories, and occasionally two females lay their eggs in the same nest and incubate them cooperatively.
Most migrating hut warblers appear already mated in the breeding area. The courtship is rather inconspicuous. It mainly consists of rows of calls and cave points of the male. It shakes in front of the cave entrance or sits with open, trembling wings on the roof of a nesting box. The pair formation is complete when the female accepts the nest box and begins cleaning it or introducing nesting material.
The breeding caves are natural tree caves, caves abandoned or taken over by woodpeckers, and nesting boxes, especially in the last 30 years. Other breeding sites, such as niches in buildings, were very rarely observed. The breeding caves are at different heights, mostly between 2 and 5 meters. There is no noticeable preference for a specific tree species. Preference is given to locations with low or sparse ground cover and a sufficient number of sitting areas. In the breeding cave, the female builds a simple bowl nest out of blades of grass and other fine and dry, plant and animal materials, the construction of which is completed in a few days. Males also often bring in nesting material, but their participation in the nest-building process is marginal overall, or is still to be understood as a courtship ritual.
Clutch and brood
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The red-throated and blue-throated warbler usually breed twice a year, or three times under particularly favorable conditions, but usually only if one of the previous broods failed. Mountain hut warblers in the northern ranges and at very high nesting sites raise only one brood per year. If the first brood fails, all three species make a second attempt at breeding. The clutches usually consist of 5 (2–7) short-elliptical, slightly bluish, unmarked eggs with an average size of 22 × 17 millimeters. Purely white eggs, usually all in one clutch, occur in all species. The eggs of the mountain hut singer are on average the most intensely colored, but a reliable identification of the species on the basis of the clutch is usually not possible. The eggs are laid at an interval of about 24 hours, from the penultimate the female incubates. In all species, only the female breeds, it is supplied with food by the male, and leaves the cave in the morning to search for food. The breeding period for all species is around 14 days (11–19). The young usually hatch within a day. Both parents feed during the nestling period. In the first few days the female spends a lot of time in the brood cavity. The nestling food consists mainly of smaller insects and caterpillars. Berries are often not yet ripe at the breeding season, but if available they are also fed. Breeding aid was mainly observed in the blue-throated warbler; it is rare in the other two species. Unpaired, mostly one-year-old males are almost always involved. In the case of second broods, young of the first brood are often helpers.
The young of the red-throated hut singer fly out after about 19 days, those of the other two species a little later. At this time they are only capable of short fluttering flights and are completely dependent on their parents. After two weeks at the earliest, they can fly longer distances and look for food independently, but they are still fed by their parents. This lead time lasts up to two months for young birds from second broods, those from first broods are often driven out of the area at the beginning of the second brood and then often join together to form roaming groups. Fledglings of the blue-throated slinger stay more often than those of the other two species in the family unit, in which they take on a helper role for the next brood.
Reproduction rate
The reproduction rate of all three species is high. There are no noticeable differences between the species. Young hatch from more than 80% of the eggs, of which over 75%, in very good conditions around 90%, fly out; on average that is between 3.5 and almost 5 young birds per brood that has started. A single pair of the blue-throated hut singer brought a total of 19 young to fly in three broods in one year.
Life expectancy
As with all wild life, mortality is highest in the first months of life; After the first survived winter and the first successfully completed train, the mortality curve also flattens out significantly for the cottage singers. The oldest red-throated and blue-throated hut warblers observed in the wild were 8 years old; hardly any data is available on the life expectancy of the mountain hut warbler.
Systematics
The hut warriors are a genus of thrushes . These are either assigned as the subfamily Turdinae of the flycatcher family (Muscicapidae), or are considered an independent family (Turdidae). The genus Myadestes, which is widespread in America and Hawaii , is considered a sister genus , while the blue-throated slugger and the red-throated slugger are sister species.
There are 3 types and 14 subspecies:
- Mountain hut warbler ( Sialia currucoides ( Bechstein , 1798) ): From Alaska in a wide belt over the Rocky Mountains southwards to the southern USA. - No subspecies
- Blue-throated hut warbler ( Sialia mexicana Swainson , 1832 ): West of the Rocky Mountains to Baja California, central and southern USA to south-central Mexico. - 6 subspecies
- European Red-throated Warbler ( Sialia sialis ( Linnaeus , 1758) ): East of the Rocky Mountains, Bermuda , Mexico, Central America. - 8 subspecies
Endangerment and existence
None of the three species is currently endangered in their entirety: these are either stable or increasing slightly. Regional and mostly only temporary declines in stocks are mainly due to modern forest management, the dead wood is largely removed from the forests and thus breeding opportunities and food sources are reduced. The increasingly intensified prevention of forest fires and their more effective control, as well as the large-scale use of insecticides , which is still practiced, regionally thin out stocks of the blue-throated and mountain hut warbler in particular. On the other hand, the very frequent use of nesting boxes, especially in Canada and the USA, and the intensive winter feeding have led to the fact that cottage warblers are now a common bird there, and care must be taken that the massive protective measures do not come at the expense of biodiversity .
The population of the Rotkehl-Hüttensänger is estimated at 10, that of the mountain hut singer at 5.2 and that of the blue-throated hut singer at 1.4 million individuals.
literature
- Patricia Adair Gowaty, Jonathan H. Plissner: Eastern Bluebird (Sialia sialis) . In: The Birds of North America Online. Cornell Lab of Ornithology, retrieved from Birds of North America Online , Ithaca 1998.
- Judith A. Guinan, Patricia A. Gowaty, Elsie K. Eltzroth: Western Bluebird (Sialia mexicana) . In: The Birds of North America Online. Cornell Lab of Ornithology, retrieved from Birds of North America Online , Ithaca 2008.
- Harry W. Power, Michael P. Lombardo: Mountain Bluebird (Sialia currucoides) . In: The Birds of North America Online. Cornell Lab of Ornithology, retrieved from Birds of North America Online , Ithaca 1998.
Web links
- xeno-canto: Sound recordings - Eastern Bluebird ( Sialia sialis )
- xeno-canto: Sound recordings - Western Bluebird ( Sialia mexicana )
- xeno-canto: Sound recordings - Mountain Bluebird ( Sialia currucoides )
Individual evidence
- ↑ a b Sialia in the IUCN Red List of Threatened Species .
- ^ Gary Voelker, John Klicka: Systematics of Zoothera thrushes, and a synthesis of true thrush molecular systematic relationships . In: Molecular Phylogenetics and Evolution. 49 (2008), pp. 377-381.
- ^ Eastern Bluebird Sialia sialis. On: Birdlife international. pdf engl.
- ↑ Mountain Bluebird Sialia currucoides. On: Birdlife international. pdf engl.
- ↑ Western Bluebird Sialia mexicana. On: Birdlife international. pdf engl.
- Patricia Adair Gowaty, Jonathan H. Plissner: Eastern Bluebird (Sialia sialis) . In: The Birds of North America Online. Cornell Lab of Ornithology, retrieved from Birds of North America Online , Ithaca 1998.
- Judith A. Guinan, Patricia A. Gowaty, Elsie K. Eltzroth: Western Bluebird (Sialia mexicana) . In: The Birds of North America Online. Cornell Lab of Ornithology, retrieved from Birds of North America Online , Ithaca 2008.
- Harry W. Power, Michael P. Lombardo: Mountain Bluebird (Sialia currucoides) . In: The Birds of North America Online. Cornell Lab of Ornithology, retrieved from Birds of North America Online , Ithaca 1998.