Burmese strangler
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Burmese strangler ( Lanius collurioides ), male |
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| Lanius collurioides | ||||||||||||
| Lesson , 1831 |
The Burmese shrike ( Lanius collurioides ) 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 common in Myanmar , southern China , parts of Thailand and Vietnam , as well as Cambodia and Laos . To the west, spatially separated by the delta of the Ganges and Brahmaputra , is the area of distribution of the red-shouldered shrike , which is considered to be the sister species of the Burmese shrike.
Like many other shrike species, the species feeds primarily on insects and other invertebrates . The proportion of vertebrates such as young mice, nestlings and lizards seems to be slightly larger in this species than in the red-shouldered shrike. The migratory behavior of the species is inconsistent: There is a population from almost exclusively migrating Burma stranglers to largely resident ones, with all the gradations that can lie in between. Wintering areas and breeding areas further south overlap widely. A distinction is made between two subspecies, none of which are currently listed in a hazard level of the IUCN . The Burmese strangler is one of the worst researched strangler species.
Appearance
With a length of 20 centimeters, the Burmese strangler is slightly larger than a red backed killer , but it is slimmer than this and therefore a little lighter with an average of 26 grams. It is slightly larger than its sister species, but a good 20% heavier than this. The species is very similar to the red-shouldered shrike, but overall it is a bit darker, less contrasting in color. There is no gender dimorphism in terms of height and weight, in terms of coloration it is very low. In some females, the black headband is a bit narrower and they are overall a bit paler and more washed out than the males. Females often show white nasal feathers above the base of their beak and a fine banding in the chest area can be indistinctly visible.
The typical black face mask covers the forehead and runs laterally over the eyes and cheeks to the neck. In males of the nominate form it can only be clearly recognized in favorable light conditions, in the somewhat lighter females it usually stands out more clearly from the rest of the head plumage. In the dark-headed subspecies L. c. nigricapillus it is almost completely assimilated by the dark forehead and crown cap. The rest of the head is dark gray, in L. c. nigricapillus almost black, the throat whitish. The dark gray color of the neck and upper back gradually merges into the reddish chestnut brown of the coat and back. The top of the wings is dark brown, the rump is brownish, the central feathers of the tiered tail are black, the outer ones white. The wings are black, the hand wings are white in the basal section, which creates a small white wing mirror when the bird is sitting and a white wing field when it is in flight. The belly is almost pure white, slightly pink on the sides and towards the flanks. The under tail-coverts are white, as are the underside of the tail-feathers, some of which are bordered with black at the top. The rather small hooked bill is dark gray, black towards the tip, legs and toes are gray-black, the iris is reddish brown. Besides the already mentioned differences in the color of the head, the subspecies L. c. nigricapillus darker and dull brown in color on the upper side. There are usually no field ornithological differences between the sexes of this subspecies.
Juveniles largely correspond to the color scheme of other medium-sized, reddish-brown strangler species, so they are very difficult to identify in the field. The head is banded and spotted brownish on a gray background, the mask is indicated as a brownish spot around the ears. The coat, back and rump are also gray-brown with distinct bands. The tail is brown, the outer control feathers are a little lighter. The bright wing field is not yet developed or only weakly indicated. The underside is matt white to yellow-brown with distinct dark bands on the chest and flanks. Immature resemble colored young females, but the banding of the juvenile plumage is still clearly visible in them. As far as is known, adult Burma stranglers moult their entire plumage only once a year between August and October. Juveniles molt parts of their plumage in autumn.
Vocalizations
There are relatively few analyzes of vocal expressions of this type. Panov noticed surprisingly large differences to the singing of the red-shouldered shrike and saw clear similarities to that of the chess shrike . The singing is a quiet, persistent chatter with lots of melodic passages, but also whistling and squashed-looking elements. As with many species of shrike, song elements from other bird species are incorporated into the song, so that the songs of different individuals can sound very different. The calls are a high-pitched, jay-like screeching in a row.
Distribution, habitat and migrations
strangler reddish-brown: Mainly breeding areas that are abandoned outside the breeding season
olive: wintering areas in the northern part also breeding areas of largely resident populations
dark brown: breeding area of the largely resident subspecies L. c. nigricapillus
The Burmese strangler is a breeding bird of southern, mainland East Asia. The exact distribution limits are unclear, especially in the extreme northwest of the distribution area and in southern China, but especially in Cambodia. The species breeds in Myanmar (south to the central Tenasserim Mountains ), in west and central Yunnan , in east and south Guizhou , in south-west Guangdong , as well as in north-west and west Thailand, Laos, in east Cambodia as well in Vietnam with the probable exception of the southernmost part. Breeding occurrences in the extreme northeast of India are considered possible, but are not certain, the same applies to possible breeding occurrences in eastern Cambodia, as well as winter occurrences in the rest of the state. The species is completely separated from the sister species in the breeding areas; in the westernmost wintering areas of the Burmese shrike, there could occasionally be sympathy with the red-shouldered shrike, especially in the area of the Ganges-Brahmaputra delta .
The Burmese strangler inhabits the coastal plains and altitudes up to 1,800 meters in Myanmar, 2,400 meters in southern Vietnam and 2,500 meters in southern China. The altitudes between 600 and 1830 meters seem to be preferred. Burmese stranglers occur in the semi-arid bushland as well as in open forest areas, they colonize tree-lined avenues along roads or paths, tree-lined or bushy field edges, and penetrate into the outskirts of human settlements. Almost all information on settlement densities and space requirements is missing. At least locally, however, quite high population densities can be achieved: 4 breeding pairs were found on a 400 meter long measuring section along the base of a hill.
The migratory behavior of the Burmese strangler has not been researched in detail. Relatively dense winter occurrences in the south, south-east, partly also west and south-west of the distribution area show that many populations from other breeding areas leave these after the breeding season. Most of the birds of northern Myanmar leave the breeding areas after the breeding season in June / July and move to the plains of the south and the Malay Peninsula southwards to Prachuap Khiri Khan . Only a few populations, especially those in the lowlands, remain in the breeding area. The southern Chinese Burma stranglers and those from the north and northwest of Vietnam are largely resident birds that only undertake small-scale migrations. So the birds of the high altitudes migrate to lower lying areas. The same applies to the populations of the subspecies L. c. nigricapillus .
Food and subsistence
As with all other small and medium-sized shrike species, insects make up the predominant part of the diet, both in terms of the number and total weight of the prey animals. All easily accessible insect species above a certain value, which is decisive for the energy efficiency of the species, are captured. For the Burmese strangler, locusts seem to be a particularly important part of their diet. During the mass swarming of termites , several individuals were observed feeding on a termite den. Small vertebrates such as mice , geckos and nestlings also belong to the food repertoire of the species, but are not significant in terms of quantity or weight.
Burmese stranglers mainly hunt from a hide that is two meters above the ground. If they spot a prey animal, hit it on the ground and eat it there, or return with the prey animal to the same or another hide. On the ground they hop on both legs; It is not known whether they pursue prey over long distances or even hunt them on the ground. It is believed that Burmese stranglers create skittles, but this has not yet been documented for this species.
Behavior and Breeding Biology
Detailed studies are lacking on general behavior as well as courtship and breeding behavior. Burmese stranglers are diurnal and territorial. Smaller assemblies of several individuals were observed without it becoming clear whether they were family groups or the assemblies of adult birds that are not infrequently observed in stranglers.
The nest is very variable in size. It is built exclusively from soft materials, especially grass, using all kinds of human waste, such as fabric scraps and plastic, mostly at heights between 1.5 and 3 meters, but occasionally also significantly higher in bushes or trees, especially spruce and pine . Inside it is mainly designed with feathers and outside often camouflaged with cobwebs. The clutch consists of 3–6 (mostly 5) eggs of greenish white, yellowish or dirty white basic color, which are entirely, but especially at the pointed end, yellow-brownish speckled. No information is available on the incubation period, nestling time and breeding success.
The breeding season extends from March to June. The main opening times are in Myanmar in April and May, in southern China in June. In the south and in the lowlands of the north, two annual broods are probably the rule.
Systematics
The exact relationship of the Burmese strangler within the genus Lanius is unclear. It is likely that the red-shouldered shrike is a sister species. Whether the two are to be placed in the vicinity of the Lanius collurio - Lanius phoenicuroides - Lanius isabellinus - group is questionable despite some similarities due to essential differences in terms of song and behavior. There are currently two well-differentiated subspecies (description in the Appearance chapter ):
Existence and endangerment
Quantitative data are not available and population trends are also absent. For some regions, e.g. B. Cambodia practically lacks all the data that would enable a reliable population assessment. At least regionally, such as in some parts of Vietnam, Myanmar, Thailand and Laos, the species seems to be quite common. Apparently, this does not apply to southern China, where the Burmese strangler is seen less often. This species of strangler could benefit from the widespread deforestation of primary forests in their habitat ; the regrowing, often eroded bush regions or light secondary forests offer new habitats that accommodate the species. The Burmese strangler is classified by the IUCN as harmless (LC = least concern ).
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 .
- R. Yosef, International Shrike Working Group, E. de Juana: Bay-backed Shrike (Lanius vittatus). In: J. del Hoyo, A. Elliott, J. Sargatal, DA Christie, E. de Juana (Eds.): Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona 2013. (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 .
Individual evidence
- ↑ a b Lanius collurioides in the IUCN Red List of Threatened Species 2014.2. Listed by: BirdLife International, 2012. Retrieved November 12, 2014.
- ↑ a b c d E. N. Panov: The True Shrikes (Laniidae) ... 2011, p. 704.
- ↑ a b c d e T. Harris, K. Franklin: Shrikes & Bush-Shrikes ... 2000, p. 205.
- ↑ a b c d e f R. Yosef, International Shrike Working Group (2008). Burmese Shrike (Lanius collurioides). In: J. del Hoyo, A. Elliott, J. Sargatal, DA Christie, E. de Juana (Eds.): Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona 2013. (retrieved from http://www.hbw.com/node/60473 on November 6, 2014).
- ^ A b E. N. Panov: The True Shrikes (Laniidae) ... 2011, p. 707.
- ↑ a b c d e f g h i T. Harris, K. Franklin: Shrikes & Bush-Shrikes ... 2000, p. 206.
- ↑ EN Panov: The True Shrikes (Laniidae) ... 2011, p. 711.
- ↑ xeno-canto: Sound recordings - Burmese Shrike ( Lanius collurioides )
- ↑ EN Panov: The True Shrikes (Laniidae) ... 2011, p. 701.
- ^ A b E. N. Panov: The True Shrikes (Laniidae) ... 2011, pp. 705-706.
