Tibetan strangler

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Tibetan strangler
Tibetan Shrike (Lanius tephronotus), male

Tibetan Shrike ( Lanius tephronotus ), male

Systematics
Order : Passerines (Passeriformes)
Subordination : Songbirds (passeri)
Superfamily : Corvoidea
Family : Shrike (Laniidae)
Genre : Real strangler ( Lanius )
Type : Tibetan strangler
Scientific name
Lanius tephronotus
( Vigors , 1831)

The Tibetan shrike ( Lanius tephronotus ) is a songbird belonging to the genus of the real shrike ( Lanius ) within the family of the shrike (Laniidae). The medium-sized strangler species is widespread from Kashmir through northern India and the small Himalayan states northeast and east to central and southern China . The winter roosts of the part migrant are mostly in lower regions, but spatially close to the breeding areas, but partly also south, but especially south-east of them in India, Bangladesh and the northern and central Indochina . In addition to the subspecies of the wedge-tailed shrike Lanius sphenocercus giganteus , with which the Tibetan shrike occurs sympathetically in the easternmost part of Tibet , it is the only species of shrike that breeds exclusively in regions above 2200 meters, but mostly at significantly higher altitudes near or above the regional tree lines .

Like many other shrike species, the species feeds primarily on insects and other invertebrates , as well as vertebrates such as young mice, nestlings , lizards and frogs . Tibetan stranglers move to lower altitudes in winter or migrate south or south-east.

The relationship of the species within the East Palaearctic representatives of the genus has not been sufficiently clarified. The chess shrike is considered to be a very closely related species and is also considered conspecific by some taxonomists . This is especially true for the subspecies L. t. lahulensis , which is considered to be a stabilized hybrid of Lanius schach erythronotus × Lanius tephronotus . Neither of the two currently recognized subspecies is listed by the IUCN in a hazard level (LC = least concern ).

Appearance

Wintering Tibetan shrike in the Khao Yai National Park in Thailand
Intensely colored Tibetan shrike ( Guizhou , China)

The Tibetan shrike is a medium-sized type of shrike, mainly gray and black on the upper side and whitish-colored on the underside. In flight it shows no or almost no white coloring elements on the upper side. With a body length of 22–23 centimeters, it is about the same size as a song thrush and weighs between 39 and 54 grams, with females of the same height appearing to be on average slightly heavier than males. There is no color dimorphism.

In its high alpine breeding area, the species is not to be confused with any other shrike, but outside the breeding season with gray-headed subspecies of the chess shrike, especially with the subspecies Lanius schach caniceps . Chess stranglers are somewhat larger and much more long-tailed, the gray on top is lighter, the reddish-brown color of the rump is more intense and extensive. In addition, the white wing field of the chess shrike in the Tibetan shrike is very small or does not exist at all. The range of this species is completely separated from the generally very similar Philippines shrike.

The head, neck, shoulders, coat and back are uniform and unspecified, slate-gray, with the color intensity differing individually and between the subspecies. The black mask typical of a strangler is connected very narrowly over the base of the beak and runs - widening - over the eyes to over the ear covers. It often has a fine white border towards the top. The upper wing covers and the wings are black, most of the coverts and some of the umbrella feathers and arm wings are lined with light reddish brown or whitish. The white drawing of the basal sections of the inner hand wings, which is typical for many stranglers, is completely absent or is only very indistinctly developed, so that usually no white markings on the wings can be seen while sitting or flying. Only with the subspecies L. t. lahulensis is often designed as a wing mirror. The rump is indistinctly cinnamon-brown, the under-tail-coverts more intense reddish-brown. The control feathers are dark brown to blackish brown, most of them have a slightly lighter edge. Except for the tail, the entire underside is matt white, the sides of the chest and the flanks are quite intense reddish-cinnamon brown. The beak is mostly black, sometimes a little lighter at the base. The legs and toes are blackish, the irises of the eyes are brown.

Juvenile and immature Tibetan shrike are gray-brown on the upper side, the head plumage is finely wavy and dark, the rest of the upper side plumage is somewhat broader banded. The face mask is reduced to a small brown spot in the area of ​​the ear covers. The underside is closely banded black on a gray-white background. The rump and tail-coverts are reddish-brown and also show black banding. The beak is gray-brown.

Adult vermausern once a year from September to December, the entire plumage. The first pre-breeding moult of immature Tibetan shrike between March and April also seems to be a complete moult.

Vocalizations

Although there are similarities between the chants, especially the calls of chess stranglers and Tibetan stranglers, they differ significantly in terms of the frequency ranges. An essential alarm call is a sharp, short Tschert , uttered several times at short intervals ... Tschert , in addition to this, a sustained, jarring screeching can often be heard in aggression or dangerous situations . The singing is a persistent, quiet murmuring and chatting, with partly melodic elements, but also interspersed with whistles and atonal sequences. As is customary with strangle chants, phrases from other bird songs are woven in - differently varied and arranged.

Distribution, habitat and migrations

Distribution of the Tibetan shrike
dark green: breeding area Lanius tephronotus lahulensis
medium green: breeding area Lanius tephronotus tephronotus
brownish: non- breeding season occurrences

In addition to the subspecies of the wedge-tailed shrike Lanius sphenocercus giganteus , the Tibetan shrike is the only type of shrike that occurs exclusively in the high mountains at altitudes of at least 2200 meters. The lower limit of the brood distribution is clearly dependent on the influence and intensity of the Indian summer monsoon : the stronger these are, the higher the lower limit of the brood distribution. The highest nesting sites were found in Yunnan at altitudes around 4500 meters.

The species is distributed from central (perhaps also northern) Kashmir and probably the westernmost Xizang over Tibet , Nepal , Sikkim , Bhutan and northeastern India east and northeast to central and south-central China. In the northern and central part of the distribution area, the northern limit of distribution is 30 ° north, in the eastern part around 40 ° north. The eastern border is around 110 degrees east of latitude in Shaanxi , and it may also reach the westernmost areas of the neighboring province of Shanxi .

The wintering areas are mostly in close proximity to the breeding areas, but in correspondingly lower elevations, partly also south, but mainly south-east of them in north-eastern West Bengal , northern Bangladesh as well as in northern Thailand , northern Vietnam , Myanmar and Laos , and occasionally even further to southeast Indochina. The species also overwinters in larger cities, such as Kathmandu .

In the valley of Kali Gandaki, the Tibetan shrike is a common summer bird. The windbreak plantings at the field edges offer the species excellent breeding opportunities.

In this large distribution area, the species is nowhere widely represented, but rather restricted to high mountain areas following the landscape topography. Islands of distribution can often be 50–100 kilometers apart. Below the tree line, the Tibetan shrike lives in spacious, bush-lined clearings, loosely tree-lined slopes, secondary growth after mudslides or avalanches, cultivated land on the edge of settlements, bushy field margins and alpine pastures. In the bush zones above the tree line, it is mainly short-grass regions overgrown with sea ​​buckthorn , hedge roses or barberries that are preferred to be populated. In the high moor areas of Zoigê , the Tibetan shrike occurs in willows along rivers and in windbreaks at settlement borders.

Settlement densities and space requirements of the species cannot be described uniformly, but the Tibetan shrike can reach high population densities in some regions and represent the most common bird species in some areas, which are otherwise rather scarce. In the valley of Kali Gandaki in Mustang , where the species is very common and especially in Rosa sericea breeds -Büschen, a breeding pair in linear expansion takes up a 150-200 meter bushes strips, around the district capital of Zoige in northern Sichuan is the Tibetan shrike is the most common bird species in summer.

The migratory movements of the species are inconsistent. The majority of the Tibetan stranglers are only likely to migrate vertically from the high breeding areas to lower elevations or to visit regions with more favorable climatic conditions. However, some of the birds migrate south or south-east and are regularly found in the wintering areas mentioned above. There is no knowledge about the gender and age composition of the migrating populations. The move begins with the first persistent night frosts between mid-September and mid-October. Depending on the altitude of the breeding area, the Tibetan shrike return to the breeding grounds from the beginning of April. Wintering Tibetan stranglers are regularly observed in the Kathmandu valley between October and mid-March; in northern Myanmar, the species was observed between late September and early May.

Food and subsistence

A male Tibetan strangler in a typical upright observation position

As with most small and medium-sized shrike species, the vast majority of their food consists of insects and, to a lesser extent, other invertebrates . Among the insects, beetles , grasshoppers and crickets as well as butterflies , especially their caterpillars , are among the main prey animals. Earthworms can become a rich substitute food after prolonged rainfall, but also after the first night frosts. Vertebrates such as small mice, lizards, frogs and nestlings play only a subordinate role in the food acquisition of the species.

In an upright posture, the Tibetan shrike observes intensely for potential prey in a sector in a radius of between 10 and 15 meters from a hide usually at heights between 2 and 3 meters. If he spies one, he slides off the raised hide and hits it on the ground. The species seems to attack and prey on insects more frequently than most other stranglers. If there is an excess of prey, Tibetan stranglers build up supplies by impaling prey in thorny branches or pinching them in a fork.

behavior

There are no particularities known that would distinguish the Tibetan shrike from other small and medium-sized shrike species in its behavior. The species is diurnal and strictly territorial during the breeding season and probably also in the wintering areas. Outside of the breeding season the species lives solitary, only occasionally smaller sleeping communities have been observed. Young-fledged birds also seem to gather in small groups that last until they may move away together. During the breeding season, a breeding pair claims a territory that is vigorously defended against conspecifics. The partnership is a largely monogamous breeding season bond; To what extent loyalty to the breeding site leads to the mating of last year's partners is not known, and details of the courtship of the Tibetan strangler are also missing. It is believed that it is essentially similar to that of the closely related chess strangler.

Breeding biology

Depending on the weather and altitude, the first Tibetan stranglers appear again in the breeding area from the beginning of April, the males a few days before the females. By the end of April all available breeding sites are usually occupied, even at high altitudes. The first clutches were found in the last decade of May. The laying time extends over the whole of June and July and probably extends into August. Second broods are suspected, but have not yet been confirmed.

The nest is built in bushes, especially in hedge roses and barberries, but also in willows and other trees. It is usually low at heights between 1.5 and 2.5 meters, only rarely at higher heights of up to 8 meters. The division of labor between the sexes in nest building and its duration are not known. It is described as a messy, loosely assembled structure, while Panov characterizes it with its many protruding twigs and twigs, although it looks untidy, but overall as a compact and firmly joined structure, in which above all the inner nest layer is very finely interwoven with stalks and blades of grass soft animal wool, mostly sheep and yak wool is padded. In the vicinity of settlements, all sorts of human rubbish, recently increasingly plastic scraps, is always found in the nests. The outer diameter of the rather deep nest varies between 130 and 200 millimeters, the inner diameter averages 80 millimeters, the depth of the bowl is around 55 millimeters. Mostly only the steeply upright control feathers and the tip of the beak are visible of the breeding female.

The clutch consists of 4–6 matt white or slightly greenish haze eggs, which are brown or purple-brown spotted and spotted, especially at the blunt end, and can also have brownish purple spots distributed over the entire surface. With a weight of around 25 grams, its dimensions are on average 24.9 × 18.7 millimeters. The incubation period is 15-18 days, the nestling period, during which both parents feed the young, lasts about as long. In a relatively small study started with a sample of 24 broods, 45.8 percent were successful with at least one young bird that had flown out. The main causes of breeding losses were persistent bad weather and predation by the Altai weasel .

Systematics

Extensive studies on the systematic position of the Tibetan strangler within the genus Lanius are not available. Until recently it was considered a subspecies of the chess shrike, to which it is undoubtedly very closely related. To what extent the subspecies L. t. lahulensis is to be regarded as a stabilized hybrid with Lanius schach erythronotus or rather with Lanius schach caniceps , requires further research. Where chess shrike and Tibetan shrike occur in the same areas, their brood distribution is largely separated vertically, so that it is questionable whether there are any contact zones at all. The available molecular genetic investigations show the Tibetan shrike to be closely related to the chess shrike, but not as its sister species .

Two moderately differentiated subspecies are currently described:

  • Lanius tephronotus tephronotus ( Vigors , 1831) : Almost the entire range of the species except for the extreme north-west. No white wing markings, relatively dark gray on the top.
  • Lanius tephronotus lahulensis Koelz , 1950 : Kashmir, western Xizang to Uttar Pradesh , perhaps also westernmost Nepal. Slightly lighter gray on top, often a small white wing field.

Existence and endangerment

Both subspecies of the Tibetan strangler are currently considered harmless. Their distribution area is large, but according to the topographical conditions of their high alpine habitat, it is very fragmented. Various species of birds of prey are important as natural predators , and above all crows, especially the thick-billed crows , and the Altai weasel as nest predators . The Tibetan strangler is not persecuted by the mainly Buddhist- oriented people in his area.

etymology

Nicholas Aylward Vigors described the shrike as Collurio tephronotus . The author did not give an exact location. The specific epithet tephronotus is derived from the Greek τεφρος for ash gray and νωτος for back . The name of the subspecies lahulensis refers to the Indian district of Lahul .

literature

  • Tony Harris, Kim Franklin: Shrikes & Bush-Shrikes. Including wood-shrikes, helmet-shrikes, flycather-shrikes, philentomas, batises and wattle-eyes. Christopher Helm, London 2000, ISBN 0-7136-3861-3
  • Josep del Hoyo , Andrew Elliot, Jordi Sargatal (Eds.): Handbook of the Birds of the World. Volume 13: Penduline-Tits to Shrikes. Lynx Edicions, Barcelona 2008, ISBN 978-84-96553-45-3 .
  • Yosef, R., International Shrike Working Group & de Juana, E. (2013). Bay-backed Shrike (Lanius vittatus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, DA & de Juana, E. (eds.) (2013). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/60476 on November 4, 2014).
  • Norbert Lefranc, Tim Worfolk: Shrikes A Guide to the Shrikes of the World. Pica Press, 1997, ISBN 1-4081-3505-1 .
  • Evgenij N. Panov: The True Shrikes (Laniidae) of the World - Ecology, Behavior and Evolution. Pensoft Publishers, Sofia 2011, ISBN 978-954-642-576-8 .
  • James A. Jobling: Helm Dictionary of Scientific Bird Names . Christopher Helm, London 2010, ISBN 978-1-4081-2501-4 .
  • Nicholas Aylward Vigors: The chairman again resumed the exhibition of the Himalayan birds . In: Proceedings of the Committee of Science and Correspondence of the Zoological Society of London . tape 1 , no. 4 , 1831, p. 41-44 ( online [accessed November 19, 2014]).
  • Walter Norman Koelz: New subspecies of birds from southwestern Asia . In: American Museum novitates . No. 1452 , 1950, pp. 1–10 ( online (PDF; 755.5 kB) [accessed on July 12, 2014]).

Individual evidence

  1. ↑ EN Panov: The True Shrikes (Laniidae) ... 2011, p. 665.
  2. ↑ a b c d e f g Yosef, R., International Shrike Working Group & de Juana, E. (2014). Gray-backed Shrike (Lanius tephronotus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, DA & de Juana, E. (eds.) (2014). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/60478 on November 11, 2014) ..
  3. ↑ EN Panov: The True Shrikes (Laniidae) ... 2011, p. 666.
  4. ↑ Lanius tephronotus in the IUCN Red List of Threatened Species 2014.2. Listed by: BirdLife International, 2012. Retrieved November 12, 2014.
  5. ↑ A lot of photos, some of them good - scroll down to get an overview
  6. ↑ a b c d e f T. Harris, K. Franklin: Shrikes & Bush-Shrikes… 2000, p. 210.
  7. ↑ a b EN Panov: The True Shrikes (Laniidae) ... 2011, p. 671.
  8. ↑ a b EN Panov: The True Shrikes (Laniidae) ... 2011, p. 674.
  9. ↑ xeno-canto: Sound recordings - Gray-backed Shrike ( Lanius tephronotus )
  10. ↑ a b c d EN Panov: The True Shrikes (Laniidae) ... 2011, p. 669.
  11. ↑ a b EN Panov: The True Shrikes (Laniidae) ... 2011, pp. 667-669.
  12. ↑ EN Panov: The True Shrikes (Laniidae) ... 2011, p. 672.
  13. ↑ a b EN Panov: The True Shrikes (Laniidae) ... 2011, p. 673.
  14. ^ A b T. Harris, K. Franklin: Shrikes & Bush-Shrikes ... 2000, p. 211.
  15. ↑ a b c EN Panov: The True Shrikes (Laniidae) ... 2011, p. 670.
  16. ↑ EN Panov: The True Shrikes (Laniidae) ... 2011, pp. 670-671.
  17. ↑ a b Xin Lu, Chen Wang and Tonglei Yu: Nesting Ecology of the Gray-backed Shrike (Lanius tephronotus) in South Tibet . In: The Wilson Journal of Ornithology 122 (2): 395-398. 2010
  18. ↑ Wei Zhang, Fu-Min Lei, Gang Liang, Zuo-Hua Yin, Hong-Feng Zhao, Hong-Jian Wang and Anton Krištín: Taxonomic status of eight Asian shrike species (Lanius): phylogenetic analysis based on Cyt b and CoI gene sequences In: ACTA ORNITHOLOGICA Vol. 42 (2007) No. 2
  19. ↑ a b Nicholas Aylward Vigors, p. 43.
  20. ^ A b Walter Norman Koelz, p. 7.
  21. ↑ James A. Jobling, p. 382.

Web links

Commons : Tibetan Shrike ( Lanius tephronotus )  - Collection of images, videos and audio files