Stactolaema
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| CHT Marshall & GFL Marshall , 1870 |
Stactolaema is a genus within the African bearded family . All four species of the genus occur in Africa south of the equator . The IUCN classifies the Stactolaema species as not at risk ( least concern )without exception.
The genus used to be part of the bearded family . Today, however, the bearded birds are regarded as a paraphyletic taxon, since they would only form a monophylum if the toucans (Ramphastidae) were included . They were therefore divided into four families, which in addition to the African bearded birds include the American (Capitonidae), the Asian (Megalaimidae) and the toucan bearded birds (Semnornithidae).
Appearance
All four species are strongly built bearded birds. Similar to the bristle-beardlings , three of the species have predominantly brownish plumage. The exception to this is the olive-bearded bird, which has predominantly greenish plumage. In all four species, males and females have similar body dimensions. There is no striking sexual dimorphism .
They are relatively small and compactly built species. The wing lengths of the individual species are 8 to 9 centimeters. The beak is around two inches long. The beak length varies between 1.5 and 2.2 centimeters.
Similar plumage is only shown by the straw-headed bearded bird and the mirrored bearded bird , both of which have partially yellow feathered faces. With the straw-headed bearded bird, the forehead is pale yellow up to the middle of the top part, the rest of the top of the head is black-brown, the sides of the neck are brown and have fine white spots. The sides of the face are white up to and including the upper ear covers, the chin is pale yellow to whitish-yellow. The crown of the mirror-bearded bird is dark brown, a thin pale yellow line separates the base of the beak from the crown and continues as a stripe across the eyes. A yellowish-white line runs below the eye region. Otherwise the face is gray-black. The rest of the plumage of both species is brownish.
The white-eared bearded bird is black-brown from the forehead to the neck, the feathers of the forehead to the central part have shiny black, lanceolate tips. A white stripe runs over the eye, which widens slightly at the end and runs above the ear covers and along the front sides of the neck. The sides of the head, the throat and the chin are black, the feathers each have hair-like tips. The upper side of the body is black and has a brownish wash from the middle of the back to the upper tail-ceiling. The white-eared bearded bird is the darkest feathered Stactolaema species on the upper side of the body . However, the underside of the body is white from the breast to the coverts. The rear flanks are also white.
The olive-bearded bird is the only species among the Stactolaema that does not have any conspicuous markings: both sexes have a blackish-brown forehead, the feathers on the head sides are gray-black with green tips, the neck and throat sides are olive-colored. The top of the body is yellowish green. The control springs are yellow-green on the upper side, the nib tips and feather edges are black-brown, the spring base is generally a bit lighter and the spring shafts are matt black. On the underside, the control springs are dull yellowish green, the spring shafts pale yellowish.
Distribution area
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All four species occur in Africa south of the equator. The most westerly occurring species is the straw-headed bearded bird, whose range extends from the DR Congo to Angola and Zambia.
The other three species are native to East Africa. The olive-bearded bird, which occurs in Kenya, Tanzania, Malawi, in western Mozambique and in the South African province of Natal, has a noticeably disjoint distribution area . In Kenya and Natal it occurs at sea level, in other regions of its distribution area it lives on high plateaus up to an altitude of 2000 meters. In the mountain forests of the Udzungwa Mountains National Park , which extend up to an altitude of 2400 meters, the olive-whiskered bird has not yet been observed above 1870 meters. The distribution area of the three East African species partially overlaps. The species, however, tend to be parapatric , i. that is, they compete for either food and / or nesting holes and do not colonize the same areas at the same time. Wherever the white-eared bearded bird occurs, the olive-bearded bird is usually absent and both species influence the occurrence of the mirrored bearded bird.
All four species colonize forests or loosely tree-lined regions.
Way of life
Stactolaema species are generally socially living, territorial birds that breed in tree hollows they have made themselves. They are typically seen in small flocks that can contain up to eight individuals. The individuals in these groups are almost certainly parent birds with their adult offspring from the previous year. Basically only the parent birds breed, the other birds help, according to the current state of knowledge, with chopping the tree hole, with some species such as the white-eared bearded bird, it has been proven that they also help with the breeding and rearing of the nestlings. In the white-eared bearded bird, the participation of the helper birds in the brood means that the change between breeding birds occurs at intervals of ten to twenty minutes. The involvement of the helpers has not yet been proven in the olive-bearded bird, here the breeding intervals are around 30 minutes.
While the other birds in a flock are looking for food, in all species a bird either remains in the nesting cavity or in the immediate vicinity of the entrance to the nesting cavity. They defend the cave against brood parasites such as the small honey indicator and / or the black throat honey indicator . The straw-headed bearded bird aggressively defends the immediate area around the nesting hole from other bird species. Among the birds that he regularly drives out is the mirror-bearded bird. Smaller bearded birds such as the miombo bearded bird and the yellow-browed bearded bird are chased away by the parent birds and by one to four helpers from a radius of forty meters around the nesting hole. The much larger masked spirals , shrike species and barn swallows are also attacked by straw-headed bearded birds when they fly past or settle in the vicinity of the nesting cavity.
The diet of the Stactolaema species consists of fruits and insects. Newly hatched nestlings are initially given insects, although the feeding intervals are very short due to the helpers involved. With the straw-headed bearded bird, for example, the nestlings are fed up to 17 times an hour.
species
The following four species belong to the genus Stactolaema :
- Straw-headed bearded bird ( Stactolaema anchietae )
- White-eared bearded bird ( Stactolaema leucotis )
- Olive whisker ( Stactolaema olivacea )
- Mirror bearded bird ( Stactolaema whytii )
supporting documents
literature
- Lester L. Short, Jennifer FM Horne: Toucans, Barbets and Honeyguides - Ramphastidae, Capitonidae and Indicatoridae. Oxford University Press, Oxford 2001, ISBN 0-19-854666-1 .
Individual evidence
- ↑ a b Short et al., P. 140.
- ↑ Short et al., P. 137.
- ↑ a b Short u. a., p. 148.
- ↑ Short et al., P. 149.
- ↑ Short et al., P. 145.
