Taita Strangler
| Taita Strangler | ||||||||||||
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Adult Taita Strangler |
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| Lanius dorsalis | ||||||||||||
| Cabanis , 1878 |
The Taita shrike ( Lanius dorsalis ) is a songbird belonging to the genus of the real shrike ( Lanius ) within the family of the shrike (Laniidae).
The starling-sized , sturdy, high-contrast black, gray and white strangler species is common in eastern Africa north and south of the equator from the Republic of South Sudan south to northeastern Tanzania . it shares the northern part of its range with its sister species the Somali shrike . It lives singly or in breeding pairs in relatively dry scrubland or in acacia savannas .
Like the majority of representatives of this genus, the Taita strangler is also a hide hunter , who feeds primarily on invertebrates and occasionally on small vertebrates . The species is considered to be a resident bird , but isolated small-scale migratory movements and entries into otherwise unpopulated areas have been observed.
There is hardly any information about the distribution of the Taita strangler. There is also no detailed information on the biology of the species. Currently (2016) it is not listed in any hazard level; at least regionally it does not seem to be rare.
The German common name refers to the district in Kenya from which the type specimen comes. The species is monotypical , no subspecies are described.
Appearance
The Taita strangler is a striking, contrasting, brawny looking, rather short-tailed strangler. It measures around 21 centimeters and weighs around 50 grams. Particularly striking and characteristic is the slate-gray coat, set off in white from the black wings.
The sexual dimorphism is limited to minimal differences in color: females are imperceptibly less contrasting and often have a chestnut-brown color on their flanks, which is usually hidden by the wings of the seated bird.
In the northern part of its range, its breeding areas overlap with those of the Somali shrike, with whom it can be confused very easily. The Somali shrike is long-tailed, less massive, the gray on the back is more subdued and the white parts on the tail and wings are more extensive. Juvenile Somali stranglers are significantly lighter in color than juvenile Taita stranglers.
The forehead, crown, cheeks, nape and upper coat are black. The black face mask is largely absorbed, but can be seen as an even more saturated area from certain angles. The rest of the coat and the back are lightening slate gray towards the rump. The shoulders are white, in stark contrast to the black wings. The bases of most hand wings are white. This creates a white wing field that is almost always visible when the bird is sitting, and a conspicuous crescent-shaped pattern when it is flying. The upper tail-coverts and the rump are washed out white. The entire underside of the body is white; sometimes the throat area is slightly rusty brown. The clearly stepped tail is black in its basic color, but can appear quite light due to the individually different white components. The outer flags of the two edge feathers are mostly white, the proportion of white decreases towards the middle pair. The underside of the tail is irregularly dripped white on a dark brown ground. The mighty hooked bill is black, as are the legs. The iris is dark brown.
Young birds are gray-brown. The entire top is finely banded or spotted. Upper tail-coverts and rump are pale yellow-brown, the tail a little darker. The hand wings are edged yellow-brown towards the tip, as are some arm wings and umbrella feathers. The face mask is indicated above all in the area of the ear covers. The underside shows slight dark bands, otherwise already resembles the adult.
In short distances, Taita stranglers usually fly just above the ground with a rapid flapping frequency. The cross-country flight is wavy. The sickle-shaped white wing markings and the V-shaped, white shoulder area are striking.
Mauser
Information on moulting is largely missing. In Ethiopia , birds were spotted during the renewal of the wing and tail feathers in June .
Vocalizations
The vocalizations seem to be very diverse, but have not yet been adequately researched and documented. They are similar in some elements to those of the Northern Fiscal Strangler , but are quieter and more restrained. Short whistles and humming sounds, as well as short double- syllable tsap-tsap calls, and throaty wok-wok and knock-knock sounds reminiscent of crow calls have territorial functions . In a descending flight a flight song is evidently performed, the context of which is still unclear. The singing itself is a quiet, unmelodious mixture of hollow-sounding, cooing and jingling elements.
distribution and habitat
The Taita strangler is widespread from the south and southeast of Ethiopia and the extreme southeast of the Republic of South Sudan southwards over the extreme northeast of Uganda , central and southern Somalia , Kenya to the north and northeast of Tanzania. Kenya is almost completely populated except for the mountains in the east and a stretch of coast in the south. The northern limit of distribution is not very clear, but should be around 7 ° North, the southern one is in the lowlands of the southern Kilimanjaro area and in the drier parts of the southern Serengeti .
The species inhabits dry, open bushland and acacia savannas, as well as only loosely tree-lined marginal zones of more densely forested regions. It occurs from sea level to around 1600 meters. The species does not inhabit deserts, humid habitats and forested areas. Where Somali stranglers and Taita stranglers are common, the Somali strangler appears in the arid , loosely bushed areas. The common distribution areas between the northern fiscal strangler and the Taita strangler are separated by the preference for humid habitats by the fiscal strangler. Long-tailed shrike and Taita shrike occasionally appear in the same habitats.
The species is considered a resident bird, but post-breeding season sightings outside the breeding area make small-scale migratory movements likely. It was found south of Dar es Salaam and to the east in Kericho . At the beginning of the century a very strong incursion of Taita stranglers was observed on the Juba .
There is no information on space requirements or the size and type of territories.
Biological details
The species has not been adequately researched. Detailed information on most of the individual biological aspects is not available.
Food and subsistence
The diet of the species consists largely of invertebrates . The Taita strangler also prey on small vertebrates more rarely but regularly .
Insects dominate the invertebrates, especially grasshoppers , beetles , caterpillars and butterflies . Also spiders are an important food source. On occasion, small lizards , small snakes , no rodents and small songbirds and their nestlings are also captured. He is apparently able to hit prey animals that come close to his own body size. Parts of a young rat were found in the stomach of a Taita strangler. He probably also visits the bloodbeak weaver's colonies in order to prey on its nestlings.
Like most species of the Lanius genus, the Taita strangler is primarily a hide hunter who searches the ground for prey from a relatively upright position from a mostly exposed seat guard. If it spies a suitable prey, it slides from the hide and hits it on the ground. Smaller prey is eaten on the spot, larger prey carried back to the hide and cut up there. Much less often it hunts for swarming insects or reads prey from substrate surfaces. It has not been confirmed whether, like the Somali shrike, it impales prey.
Behavior and Breeding Biology
Like all stranglers, the Taita strangler is diurnal. The species is described as shy and difficult to observe. It lives in pairs during the breeding season, otherwise probably alone. But family groups were also found. There is no information about the extent and type of territoriality or the number of annual broods.
The breeding season is associated with the onset of the respective rainy seasons . It is in the main distribution area Kenya between March and June and December and January, in Tanzania mainly in January and June in Somalia in May. The courtship ritual probably includes a flight song, which is performed during the fall phase of a show flight. The nest is a bowl woven from grass and twigs, which is usually built inside a dense thorn bush. The clutch consists of 3 - 4 cream-colored eggs, mainly gray and brown spotted at the long end. Further details are not available.
Systematics
The Taita strangler was first described by Jean Louis Cabanis in 1878 . He differentiates the new species from Lanius humeralis and emphasizes above all the back color, which is reflected in the specific epithet dorsalis (Latin dorsum = back). The relationship of the species within the genus is not clear. The Somali shrike is regarded as a sister species due to great morphological similarities, but this assumption has not yet been confirmed by molecular genetics . No subspecies are described.
Persistence and Threat
The species does not appear in an IUCN hazard category. In places, especially in some regions of Kenya, it seems to be not uncommon. The population trend is estimated to be stable, the habitat is not directly threatened. It breeds in some national parks, such as the Buffalo Springs National Reserve and the Serengeti National Park .
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 .
- Norbert Lefranc, Tim Worfolk: Shrikes. A Guide to the Shrikes of the World. Pica Press, 1997, ISBN 1-4081-3505-1 .
- Reuven Yosef & International Shrike Working Group (2016): Taita Fiscal (Lanius) . In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, DA & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/60487 on September 14, 2016).
- 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 c d e f g h i j k T. Harris, K. Franklin: Shrikes & Bush-Shrikes… 2000, p. 171.
- ↑ a b Lanius dorsalis in the IUCN Red List of Threatened Species 2014.3. Posted by: BirdLife International, 2012. Retrieved September 14, 2016.
- ^ A b c Norbert Lefranc, Tim Worfolk: Shrikes. A Guide to the Shrikes of the World. 1997 p. 150
- ↑ a b c d e T. Harris, K. Franklin: Shrikes & Bush-Shrikes… 2000, p. 170.
- ↑ Author's note: The voice example (as of Sept. 2016) in xeno-canto can probably be assigned to the Somali strangler.
- ^ A b Norbert Lefranc, Tim Worfolk: Shrikes. A Guide to the Shrikes of the World. 1997 pp. 150-151
- ↑ a b c d Reuven Yosef & International Shrike Working Group (2016): Taita Fiscal (Lanius dorsalis) . In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, DA & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (downloaded from http://www.hbw.com/node/60487 on September 12, 2016).
- ^ A b Norbert Lefranc, Tim Worfolk: Shrikes. A Guide to the Shrikes of the World. 1997 p. 151
- ↑ First description
- ↑ Urban Olsson, Per Alström, Lars Svensson, Mansour Aliabadian, Per Sundberg: The Lanius excubitor (Aves, Passeriformes) conundrum — Taxonomic dilemma when molecular and non-molecular data tell different stories In: Molecular Phylogenetics and Evolution. (2010) Vol. 55/2, pp. 347-357.
