Yellow-beaked shrike
| Yellow-beaked shrike | ||||||||||||
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Yellow- beaked shrike ( Corvinella corvina ) |
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| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Corvinella | ||||||||||||
| Lesson , 1831 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Corvinella corvina | ||||||||||||
| ( Shaw , 1809) |
The yellow-billed shrike ( Corvinella corvina ) is the only kind of genre Corvinella within the family of the Strangler (Laniidae). The magpie shrike ( Urolestes melanoleuca ) was recently removed from this genus and placed in the likewise monotypical genus Urolestes .
The yellow-billed, long-tailed bird, which is almost uniformly brown or gray-brown on the upper side, occurs in a wide strip south of the Sahara and north of the rainforest belt from the West African Atlantic coast eastwards to Kenya . In this large distribution area, the species inhabits different habitats from dry savannahs to the fringes of tropical moist forests with a relatively high climate tolerance .
Yellow-beaked shrike live in groups of around 12 individuals, in which only a largely monogamous pair breeds. The brooding female dominates the group, most of the other group members assist with the brood. The species feeds on large insects and small vertebrates. The northern populations leave their breeding areas during the dry season and migrate south in large groups, the yellow-beaked shrike living further south are resident birds .
The yellow-beaked shrike is common locally. It is classified by the IUCN as not endangered (LC = least concern).
features
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With a total length of around 30 centimeters, the yellow-billed shrike is one of the largest species of shrike. However, 3/5 (18 centimeters) of it is on the tail. The average weight is 65 grams, which corresponds to that of the much smaller northern gray shrike . The bird, which is usually gray-brown on the top and lighter on the underside, is largely unmistakable in its large area of distribution.
Appearance
The top is darkly dashed on a brown or gray-brown background; the basic color becomes lighter towards the rump, the dotted lines more indistinct. The wings are dark brown, the arm wings are warm chestnut brown in the first third. When the bird is seated, this creates a differently clear wing field, when it is flying it is always visible as a striking, wide sickle in the last third of the wing. The dark tips of the hand wings contrast strongly against this light field. The small wing covers can be lighter in color than the rest of the upper side plumage. The head, crown and neck are reddish brown, sometimes also yellowish brown, from the base of the beak a dark mask extends over the eyes to the ear covers. With the same basic shade, the upper side coloring and the intensity of the dark dotted lines are relatively variable. The underside is washed-out white and has fine, dark dotted lines, especially on the chest and flanks, sometimes slightly banded, wavy or meshed. The flank springs are fluffy and elongated. The dark brown feathers of the strongly stepped, very long tail (outer feathers are only half as long as the central pair) have a fine, light reddish brown border; some are dotted whitish at the tip. The iris of the yellow-rimmed eyes is dark brown, the legs are gray-greenish and the distinctive hooked bill, which has a falcon tooth , is intensely yellow.
The gender dimorphism is very low. Differences in size and weight do not seem to exist, the elongated, fluffy flank plumage is differently colored: in the male this area is only slightly darker than the rest of the abdominal area, in the female it is quite strikingly dark maroon.
Young birds are darkly wavy and spotted on the upper side on a gray-brown background, the underside is also darkly wavy and flocked on a dirty white background. The dotted lines typical of adults only appear after the first full moult.
flight
The straight, mostly low flight appears hesitant and powerless. The wings are relatively short, rounded and wide, the light maroon wing mirror is distinctive. The flight silhouette is largely unmistakable due to the short, rounded wings and long tail.
Vocalizations
The vocalizations are varied, mostly loud, rough, harsh and croaking, but also quieter, whistling, chirping and babbling. Some sounds are purely noisy, but the type also has some melodic calls that are strung together and varied in many ways. Often there are loud vocal arguments between two groups at the respective territorial borders, or quieter duets between two individuals. The group members are in constant voice contact with one another, and soft calls can also be heard in flight. According to Panov, there are no similarities to the utterances of the magpie strangler, an additional argument for splitting the genus.
distribution
The species is distributed in a broad band narrowing in its easternmost section from the Atlantic coast in West Africa east to northern Uganda and western Kenya, possibly also northern Tanzania . The northern border lies in the west in southern Mauritania at about 15 ° N and approaches the equator eastwards, which is reached and crossed east of Lake Victoria . The southern border lies in the west in central Sierra Leone and runs eastward to western Kenya, excluding the rainforest areas. In the south-west, the deposits extend in areas to the Gulf of Guinea .
In this large distribution area, the species is very climate-tolerant and is able to colonize different habitats. In the north, on the edge of the Sahel zone , yellow-beaked stranglers mainly inhabit dry savannahs and sparse tree-covered open grassland, further to the south wet savannahs and woody trees that accompany rivers. The species also occurs in areas in gardens, parks and other landscape structures that have been redesigned by humans. The yellow-beaked shrike is distributed vertically from sea level in the west and southwest to about 2200 meters in the Kenyan Rift Valley .
hikes
As far as is known, most of the yellow-billed shrike living in the dry north of the range leave their breeding areas at the beginning of the dry season. Flocks of 150 or more birds migrating south have been observed in Mauritania; in southern Mali , southern Chad and southern Sudan the species is only common between October and May. The populations living further south appear to be resident birds.
Space requirements
Little information is available on the space required by the species. Yellow-beaked shrike appear to be territorial for most of the year. They claim and defend a territory averaging 18 hectares, with group and territory size being independent of each other.
behavior
Yellow-beaked shrike are noisy, conspicuous birds that also occur in close proximity to human settlements where they are not followed. The diurnal birds, whose activity range extends from sunrise to sunset, live in groups of 6–15 individuals. Within such a group, a female dominates and is the only one to breed. His partner follows in the group hierarchy. The intraspecific aggression is low; only senior females seem to compete for the ability to mate and breed. Overall, however, the group organization, its social structure, and the integration or dismigration of the young birds has not been adequately researched. The territory is defended by all group members. At the territorial boundaries, there are often disputes with neighboring groups, which are carried out with loud shouting, flapping wings and jumping around in a border bush. The group members jointly warn of enemies, especially those who fly like different species of birds of prey and crows. The whole group spends the rest periods in a bush that they fly to at dusk. The same resting place is often kept for years.
Food and subsistence
The main food of the species is insects and earthworms . Among the insects, there are many species that do not fall below a certain size and a certain minimum weight. Ants , grasshoppers , crickets , cicadas , beetles and bees predominate. In one study, beetles, grasshoppers, and hymenoptera made up 95% of the prey. Seasonally, earthworms play a not insignificant role, and small vertebrates such as lizards , frogs and young birds are rarely captured. Yellow-beaked shrike also eat fruits.
The prey is spied out from a hide and beaten on the ground. Air hunts occur occasionally. Each group member hunts for himself, only when there is a very large food supply can you see many group members gathered. Lanius- typical impaling of prey was not observed in Corvinella .
Brood
The courtship rituals of the only brooding couple are not exactly known; In any case, the extended flank springs play a role, and feed transfers have also been observed. The breeding seasons vary greatly, especially in the south, breeding can take place in all months. The regional breeding season usually begins with the onset of the rainy season. Two, sometimes three broods are the norm. Only a dominant and apparently monogamous pair breeds; competitive situations can arise between two or more females willing to breed. The nest is built by the breeding couple and a few helpers at a height of 3–6 meters in a bush. It's a rather loose, sloppy bowl with an average diameter of 95 millimeters and a depth of 44 millimeters. The construction consists of twigs and blades of grass. The clutch consists of 3–5 (2–6) yellowish-brown eggs with an average size of about 23.2 × 18.5 millimeters. It only breeds the female, which is fed by the male and some helpers during this time; the latter utter a quiet appeasement when approaching the nest. The incubation period is 16, the nestling period 18–20 days. The nestlings are provided with food by all group members, while the helpers hand the food to the dominant female, who feeds it to the young. The boys are independent after seven weeks and take on tasks in the group.
There is only one study from Ghana on breeding success . Afterwards, young birds flew out of only 25% of the eggs laid.
Systematics
The species was first described in 1809 by George Shaw and called Lanius corvinus , so crow-like Lanius ( strangler ) . The type specimen probably comes from Senegal . After the elster shrike was first described in 1831 as Lanius melanoleucus , René Primevère Lesson placed both species in a new genus, which he named Corvinella . Also Corvinella refers to the crows similarity and means little crow . After that, the systematic position of the two species, in particular the genus and their family assignment, remained the subject of scientific discussion. C. Hilary Fry et al. pointed out the fundamental differences between magpie shrike and yellow-billed shrike in 2000 and suggested the generic name Urolestes for the magpie shrike , which had been introduced by Jean Louis Cabanis in 1850 . This gave rise to the currently valid taxonomic situation with two monotypical genera Corvinella and Urolestes within the shrike family (Laniidae).
The geographical variation is small. Currently, mostly 3–5 subspecies are described, which differ slightly in terms of coloration, the streaking / stripes of the upper and lower side plumage and the extent of the chestnut-brown wing field.
- Corvinella corvina corvina (Shaw, 1809) : Senegal, Gambia and Niger . Large wing field, remains of dark stripes (not dashed lines).
- Corvinella corvina affinis Hartlaub , 1857 : Eastern part of the distribution area - upper side more gray-brown (not reddish brown), relatively small wing field.
- Corvinella corvina togoensis Neumann , 1900 : southern and central part of the distribution area. Very similar to the nominate form , with more intense dashed lines on the top.
- Corvinella corvina caliginosa Friedmann & Bowen , 1933 : Extreme northeast of the distribution area, especially south-central and southwestern South Sudan - slightly longer tail than the nominate form, very intensely dashed on top and bottom.
The subspecies C. c. chapini is not generally recognized and usually with C. c. affinis or equated with the nominate form.
Persistence and Threat
The range of the species is very large with 3.5 million km². In some regions, such as Ghana, the population is likely to increase slightly, while in East Africa it will decrease somewhat. In the long term, the now largely stable population density can only be maintained if the pesticide input is reduced, or at least not increased, and small-scale agricultural use structures in open or semi-open landscapes are preserved.
Quantitative surveys as well as supra-regional analyzes of the development of the population are missing. Mainly because of the very large distribution area, the IUCN evaluates the population with LC (= least concern) - not endangered.
literature
- del Hoyo, Elliot, Sargatal (Eds.): Handbook of the Birds of the World. Volume 13: Penduline-Tits to Shrikes Lynx Edicions, 2008, ISBN 84-96553-45-0 ( quote : HBW)
- Tony Harris, Kim Franklin: Shrikes & Bush-Shrikes. Including wood-shrikes, helmet-shrikes, flycather-shrikes, philentomas, batises and wattle-eyes. Christopher Helm, London 2000, pp. 21, 56-57, 139-142; ISBN 0-7136-3861-3 .
- 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
- ↑ Data sheet Corvinella corvina IUCN
- ^ Harris and Franklin (2000) p. 146
- ↑ Panov (2011) p. 184
- ↑ Voice files at xeno-canto
- ^ Harris and Franklin (2000) p. 145
- ^ Harris and Franklin (2000) p. 145
- ^ Harris and Franklin (2000) p. 145
- ^ Harris and Franklin (2000) p. 147
- ^ Harris and Franklin (2000) p. 146
- ^ Harris and Franklin (2000) p. 146
- ↑ HBW Vol. 13 (2008) p. 795
- ↑ James. A. Jobling: Helm Dictionary of Scientific Bird Names . Helm-London 2011. p. 153 ISBN 978-1-4081-2501-4
- ^ C. Hilary Fry, Stuart Keith and Emil K. Urban: The Birds of Africa, Volume VI: Picathartes to Oxpeckers Princeton University Press 2000 ISBN 978-0-12-137306-1
- ^ Harris and Franklin (2000) pp. 144 and 145
- ↑ HBW Vol. 13 (2008) p. 795
- ^ Harris and Franklin (2000) p. 145
- ↑ HBW Vol. 13 (2008) p. 795
