Eurocephalus
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Rüppell strangler ( Eurocephalus rueppelli ) |
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| Scientific name | ||||||||||||
| Eurocephalus | ||||||||||||
| A. Smith , 1836 |
Eurocephalus is only two kinds comprehensive genus of passerine birds in the family of the strangler . Both types of Rüppellwürger ( E. rueppelli ) and the White Crest Strangler ( E. anguitimens ) are south of the African Sahara is home. They are very closely related to each other and form a superspecies . Their quite extensive areas of distribution are spatially well separated so that no hybridization occurs.
White-headed and ruffle shrike feed on insects and other arthropods , but occasionally also eat fruit. They live in pairs, but mostly in small family groups. Both species are resident birds, but roam more widely outside of the breeding seasons, especially in extended dry seasons, which can also trigger larger migratory movements. The birds of this genus belong to the most original shrike species, they differ in some characteristics and behavior from other members of this family, but are currently counted among the Laniidae due to essential anatomical similarities as well as molecular genetic findings. However, this assignment is not entirely undisputed due to the great behavioral similarities with the spectacle stranglers (Prionopidae).
The two species are not uncommon in their range. Quantitative and population dynamic information is missing, but is the stock at the time as Least concern (LC = Least concern ) estimated. Overall, the research on Eurocephalus is still insufficient; the white-headed shrike is a little better recorded than its northern relative.
features
The two representatives of Eurocephalus are rather large stranglers with a body length of 19–24 centimeters; their weight varies between 40 and 80 grams. With a comparable size, they are on average slightly lighter than the song thrush . Compared to Lanius , they are much shorter-tailed and slightly shorter-legged. The white-headed shrike is on average slightly larger and heavier than its northern relative. They are the only stranglers with a completely white head. In their distribution areas they are largely unmistakable and, since their occurrences are spatially well separated, they cannot be confused with one another in field ornithological terms.
Both species are very similar to one another: the head, neck, throat, chest and belly are white, the rest of the plumage is dark brown. The flanks and lower part of the abdomen are light brownish or grayish brownish. The abdominal plumage is usually closed to the white rump by a dark, often black feather region. The shoulders, cloak and back are gray-brown in the white-headed shrike, only slightly lighter than the rest of the upper side in the low-back shrike; the rump is white in the latter, gray-brown in the white-headed shrike. The wings are dark brown to blackish on the top and bottom, the outermost of the large arm covers are also colored. The black mask, which is typical of a strangler, extends from the base of the beak to the neck, whereby it widens strongly behind the eyes over the ear covers to the neck. The mighty hooked bill of adult birds is black, the legs are dark gray or dark brown, the iris almost black. The sexes do not differ in color, size or weight.
Young birds moult into adult plumage when they are one year old before their first brood. Until then, they differ from adults mainly in their spotted, dull-brown plumage, the not yet fully developed face mask and the less pronounced white components. Young black shrike have a brown head, in young white-headed shrike it is already whitish. Adult birds, like most non-migrating stranglers, completely change their plumage once a year after breeding.
The flight is straight, rather slow, with flat, fast wing beats, interrupted by short gliding phases in which the rounded wings are held in a slight V-position. In flight, the white rump is conspicuous in the Rüppell strangler.
The vocalizations are diverse and their complexity has not yet been adequately researched. They also differ little between the two species, in the Rüppell shrike the elements are ranked a little faster. The sound characteristics are loud, rough, sometimes nasal. Melodious, grumbling, panting, squeaky and shrill screeching elements predominate. In addition, quieter chattering and chattering rows of calls can be heard. Usually the representatives of this genre call in the social association, the family group, or duet with the partner. According to Panov, the vocalizations of both species differ significantly from those of the stranglers from the genus Lanius .
distribution and habitat
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Both types of Eurocephalus are native to sub-Saharan Africa. The northern species, the Rüppellstrike, inhabits areas from southern South Sudan and northeastern Ethiopia via Somalia , Kenya and Tanzania south to the northern border of Mozambique . To the west, the distribution area is split up like islands, reaching the east coast of Lake Victoria and even further west some isolated distribution areas in Uganda and Tanzania. To the east it is bounded by the Indian Ocean . The spatially completely separate living areas of the southern species extend from the Atlantic Ocean in Angola via Botswana and Zimbabwe to the coast of the Indian Ocean in southern Mozambique. The southern borders are in central Namibia as well as in northern South Africa , in the north about the middle reaches of the Zambezi .
Open, largely dry bushland, acacia steppes, Commiphora bushland , in the south also baobab stocks and forest savannas of the miombo type are inhabited . In desert-like regions, the occurrence is limited to bushy or sparsely tree-covered marginal areas of temporary watercourses. Occasionally these stranglers breed in gardens and other human-designed habitats. Vertically, the distribution extends from sea level to altitudes of 1400 meters, in Kenya occasionally over 2200 meters. In South Africa the high veld remains unpopulated, while the white-headed shrike is common in the low veld and bushveld .
behavior
Both species live in pairs, but more often in family groups of up to 12 individuals. Outside the breeding season, the groups can have even more members. The couples or groups claim a territory that is demarcated and defended primarily by calls. Only one information from South Africa is available on the size of the territory with around 200 hectares.
The Eurocephalus species, like most stranglers, hunt as perch hunters and beat their prey on the ground. Air hunts and prey capture on foot also occur. Reading of parasites from ungulates has been found at times . Searching trunks and branches is also part of the prey search scheme of Eurocephalus ; these birds occasionally hang upside down on thin branches to inspect the underside of the leaves, a behavior that has not been observed in stranglers of the genus Lanius . Prey are mainly large insects such as crickets , beetles , butterflies and grasshoppers , but other arthropods, including part disdained by other birds hundred- and millipedes are eaten. Both types eat fruit seasonally.
The breeding seasons vary widely and seem to be related to the occurrence of rainfall. While the Rüppell shrike apparently broods regularly at least twice a year, no multiple broods are known of the white-headed shrike. Breeding aid is common in the genus Eurocephalus , and, as oversized clutches suggest, intraspecific brood parasitism is not uncommon. Similar to other bird species that practice breeding assistance, only one monogamous pair breeds in groups of white-headed strangles, while the other group members assist. In addition, however, there are also pairs without brood assistants. In contrast to the rather sloppily built nests of most other shrike, the nest of the Eurocephalus species is a carefully and finely built small bowl made of grass and stalks, which is padded with animal hair on the inside and covered with cobwebs on the outside so that it has a silvery appearance and difficult to discover. It is usually very high in a fork of a branch. A normal clutch contains 3–4 eggs, if two (or more?) Females lay in one nest, the clutch size can be 7–10 eggs. The breeding period for the white-headed shrike is 18–20 days, but it is unknown for the black shrike. It is not known how the family systems are established, but the boys seem to remain in the family for a few months after they fledged.
Systematics
Eurocephalus was first described as E. anguitimens by Andrew Smith in 1836 on the basis of a specimen collected in South Africa . The generic epithet refers to the relatively large head of this species. ( Greek ευρύς = broad, κεφαλή = head ) The sister species was first described in 1853 by Charles Lucien Jules Laurent Bonaparte .
Mainly due to anatomical similarities and similarities in behavior, the two Eurocephalus species were assigned to the spectacle stranglers, which, depending on scientific opinion, were understood as a separate family Prionopidae, or as Prionopinae formed a subfamily of the Laniidae. The similarities between Eurocephalus and the spectacle stranglers exist in their behavior (nest building, brood aid, family groups), in their vocalizations, as well as in anatomical details (horn scales also on the sides of the legs, similar leg muscles) However, recent behavioral and anatomical studies have shown a closer relationship from Eurocephalus to the family of stranglers (Laniidae), which was finally confirmed by molecular genetic findings. Nevertheless, the position of Eurocephalus as the fourth genus next to Lanius , Corvinella and Urolestes within the family Laniidae is not out of discussion. Panov sees such great similarities with the spectacle stranglers, especially in their behavior and vocalizations, that he advocates another revision of the taxonomic classification. It is believed that Eurocephalus is a genus of very primitive shrike that go back to a direct, crow-like ancestor. The genus consists of two poorly differentiated species, the ruffian shrike ( E. ruepelli ) and the white- fronted shrike ( E. anguitimens ). Two subspecies are recognized from both.
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- Eurocephalus ruepelli Bonaparte, 1853
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Eurocephalus r. ruepelli Bonaparte, 1853 : South Sudan, western part of southern Ethiopia, Kenya except the northeast, as well as northern and central Tanzania.
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Eurocephalus r. Erlangeri Zedlitz , 1913 : Central and Southeast Ethiopia, Northeast Kenya and the outermost areas of Northwest, Central and South Somalia. The only difference between the two subspecies is their average size, with E. r. Erlangeri is slightly larger than the nominate form .
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Eurocephalus r. ruepelli Bonaparte, 1853 : South Sudan, western part of southern Ethiopia, Kenya except the northeast, as well as northern and central Tanzania.
- Eurocephalus anguitimens Smith , 1836
- Eurocephalus a. anguitimens Smith, 1836 : Southwest and southern Angola, northern and northeastern Namibia eastwards to Botswana, extreme Südsambia and Limpopoprovinz the Republic of South Africa.
- Eurocephalus a. niveus Clancey , 1965 : Southeast Zimbabwe and adjacent Southwest Mozambique, southwards to the eastern sections of the Limpopo Province and North Swaziland . The differences between the two subspecies are small. E. a. niveus is lighter on the upper side than E. a. anguitimens .
Persistence and Threat
Quantitative surveys as well as studies on the development of the population are not available; there is also a lack of concrete threats. Both species are considered common, at least locally. Due to these facts and the relatively large areas of distribution, which are still largely unaffected by human intervention, the population of Eurocephalus is regarded as safe.
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 (quoted: 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
- ↑ a b c HBW (2008) p. 732
- ↑ a b c d Harris (2000) p. 21
- ↑ Panov (2011) p. 166
- ↑ IUCN - E.anguitimens and IUCN - E. rueppelli
- ↑ Harris (2000) pp. 139 and 140
- ↑ HBW (2008) p. 738
- ↑ Panov (2011) p. 165
- ↑ Sound examples at xeno-canto
- ↑ Harris (2000) p. 139
- ↑ a b c HBW (2008) p. 796
- ↑ Harris (2008) pp. 139 and 141
- ↑ HBW (2008) p. 746
- ↑ a b Harris (2000) p. 140
- ↑ HBW (2008) pp. 796 and 755
- ↑ Harris (2000) pp. 139-141
- ↑ Panov (2011) p. 160
- ↑ Harris (2000) pp. 140 and 142
- ↑ James. A. Jobling: Helm Dictionary of Scientific Bird Names . Helm-London 2011. p. 153 ISBN 978-1-4081-2501-4
- ↑ Note: Urolestes emerged from the splitting of Corvinella into two monotypical genera
- ↑ Panov (2011) pp. 155-166
- ↑ HBW (2008) pp. 795 and 796
