Palm Swift
| Palm Swift | ||||||||||
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Palm swift in Johannesburg , South Africa |
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Cypsiurus parvus | ||||||||||
| ( Lichtenstein , 1823) |
The palm swift ( Cypsiurus parvus ) is a species of bird from the family of the sailors (Apodidae). It is a fairly small sailor who in Africa south of the Sahara is widespread, and he comes to Madagascar and southwest of the Arabian Peninsula before. The species is very common near palm trees, where the nesting sites are also. The nest, which is mainly built on almost vertical leaf sections of the palm fronds , is quite easily accessible to nest robbers compared to the nests of other sailors. The eggs are glued to the nest with saliva to keep them from falling out in gusts of wind.
In southern Africa, area expansions have been observed since the 1930s, and stocks seem to be increasing slightly. The species is considered harmless. Some authors consider the second representative of the genus Cypsiurus , the Bengal Swift ( C. balasiensis ), to be conspecific .
features
The body length is 16 centimeters, with up to 9 centimeters more than half of the long tail. The weight is between 10 and 18 grams, on average 13 grams. The shape is strongly reminiscent of the Apus species, but the palm-swift is slimmer, the long wings are narrower and the forked tail is longer. The tail fork is very deep with an average of 60 millimeters. Usually the tail is kept closed and appears as a slender, pointed thorn. The plumage is predominantly gray-brown and in contrast to the representatives of the genus Apus, there are no obvious features. The top is darker, especially on the more olive instead of gray-brown wings. The throat is the brightest area on the lighter underside, but the contrast is much weaker than that of the Apus species. The flight seems hectic and unsteady, often in tight circles around the favored palm trees, with irregular loud calls.
Males are on average paler in color than females and show more white on the throat, but this feature is hardly sufficient to distinguish between the sexes in the field. In young birds the outer are feathers more rounded, and the tail fork is less deep.
The palm-swift is extremely shouting. Often a chattering call can be heard, which is not unlike that of the house sailor , a loud "si-si-si-su-su", which is repeated, whereby the duration of the individual call cascades varies. This chatter can often be heard while searching for food, but most vigorously near the nest.
Spreading and migrations
The extensive African distribution area begins south of the Sahara, the northern border of the area extends from Senegal in the west to the northwest of Ethiopia , whereby the species is absent in the rest of Ethiopia and the Horn of Africa . The southern border of the area extends from the extreme southwest of Angola , across the northeast of Namibia , the north of Botswana , across the south of Zimbabwe to Mozambique . Presumably since the 1930s, the palm swift has expanded its African range further south, namely in central Namibia and east in Botswana and South Africa , where the species is now found south almost to the Orange .
The species is also found in the lowlands of Madagascar and the Comoros . There is also an isolated occurrence in the southwest of the Arabian Peninsula in the Saudi Arabian province of Asir and in the west of Yemen .
The palm-swift is considered to be a resident bird in almost the entire distribution area , in the southernmost part of the South African distribution area the species is only found in summer. Various sightings outside of the known distribution area are interpreted as potential area expansions.
habitat
The species shows a close bond with palm trees and especially with fan palms , in which the nests are built. It is therefore found in all areas where there are palm trees, which includes some very dry areas as well as the rainforest . The palm swift is also found in villages and large cities, showing a preference for parks . In South Africa, the Washingtonia palms imported from the southwest of the USA are also widely accepted and are likely to have played an important role in the recent expansion of the area. Feather-leaved palms, such as date palms , are apparently rarely used.
The palm-swift occurs predominantly in the lowlands, mainly up to an altitude of 1400 meters. In Madagascar the upper limit is 1100 meters, in Kenya broods have been found up to 1800 meters.
Behavior and food acquisition
Palm swifts are often found in smaller groups; in Kariba in Zimbabwe , a group size of four to eight individuals has been determined. Mixed swarms of maiden swallows ( Cecropis abyssinica ) and red capped terns ( Hirundo smithii ) as well as bat swifts ( Neafrapus boehmi ) were observed when foraging for food . Palm swifts feed on small animals that are caught in the air. They are mostly located at a height of less than 20 meters above the ground, which is the lowest area in comparison to the similarly feeding birds. If the upper layers of the air are not occupied by other species, the palm swift also searches for food at higher altitudes. The palm swift is active the longest at dusk in South Africa, where food acquisition overlaps with that of bats .
In 32 of the stomachs examined, mainly two- winged birds , winged ants and termite stages and beetles were found.
Reproduction
In most of the distribution area, the palm swift breeds all year round, with a focus on the warmer seasons. The species breeds in colonies, but also in isolation. The nesting sites are mainly in palm trees, but man-made nesting sites such as girder structures on bridges are also used. Mainly plant material is used as nesting material, especially cotton fibers if available, but also soft feathers. The components are stuck together with saliva. The nest consists initially of a 45 to 120 millimeter high rear wall, which is usually attached to an almost vertical leaf section of a withered or fresh palm frond, in places where there is good protection from rain. In Washingtonia palm trees , the attachment is on the trunk between two sheets of approaches. A flat bowl with a diameter of 45 to 120 millimeters protrudes at a distance of about 4 to 15 millimeters from this rear wall. Although the immediate vicinity of the nest offers little free space, palm-swifts need a free corridor of around 40 meters around the palm, which allows them to approach close to the ground. Only under the palm do they come up steeply into the palm branch. In parts of the South African range in which Washingtonia robusta is used, the palm swifts can be displaced by the larger Cape swifts ( Apus barbatus ) and Damara swifts ( Apus bradfieldi ), which also use these trees.
Copulation takes place in the nest. In 1996, however, two palm swifts were observed in Ficksburg , South Africa, who for half an hour tumbled to the ground almost every minute with body contact from a palm tree like flying seeds in a spiral. Just before reaching the bottom, the birds parted and flew back into the palm. It is not clear whether this was actually copulation in the air or territorial disputes. Anyway, the end of the other sailors species, especially the is swift , Luftbegattungen described significantly different.
The clutch usually consists of two eggs, but can also consist of one or three. The average egg size is 19.2 × 12.6 millimeters. The first egg is laid about 10 days after the nest building has started. The eggs are stuck to the nest with saliva, as the shallow shell of the nest would not offer sufficient support if the palm fronds were moved by the wind. The incubation time is around 20 days. The brooding takes place quite irregularly, the change from intensive incubation and breeding breaks does not seem to depend on the weather. The newly hatched nestlings are pressed tightly to the nest by the adult birds, probably to keep them from falling out. The nestling period is approximately between 31 and 33 days. Both sexes participate equally in the breeding business.
Since the nests are quite accessible for nest robbers compared to the other sailors, the breeding success of the palm swift is comparatively low. In various investigations, between an average of 0.3 and an average of 1.9 fledging young people were counted per breeding attempt.
Enemies
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For a sailor, the palm swift has an unusually large number of predators among the birds due to its exposed nesting places , for example the Schikrasperber ( Accipiter badius ). Even the red-winged starfish ( Onychognathus morio ) manage to beat adult palm-swifts at the nesting site. Eggs and nestlings are captured by stranglers or various crows , and nestlings also by the Fleckenuhu ( Bubo africanus ).
Existence and endangerment
The palm swift occurs regularly in the entire distribution area, in many places also frequently. The expansion of the area in southern Africa has continued around the 1930s, but the advance of elephants westward into the Kavango region in Namibia in connection with the frequent bushfires there could decimate the palm populations and thus locally endanger the populations of the palm swift. The settlement of alien palm species, on the other hand, seems to open up new areas for the palm sailor, especially in the suburbs.
BirdLife International estimates the size of the range to be approximately 16.3 million square kilometers, and it is assumed that the population will increase. Therefore the species is classified as safe.
Systematics
The two species of the genus Cypsiurus , i.e. the palm and bengal swift ( C. balasiensis ), form a superspecies and are also considered conspecific by some authors . Both types are in the same way from the the Mallophaga counting ectoparasites of the species Dennyus infested in particular occurs Dennyus cypsiurus both on. However, the differences that RK Brooke noted in 1972 in the plumage of the young birds and in the structure of the tail justify viewing palm and Bengal swifts as separate species. Brooke also suggested that the Malagasy subspecies C. p. gracilis of the palm swift to be treated as a separate species, this point of view has not yet been confirmed due to a lack of appropriate studies.
A total of eight subspecies are distinguished:
- C. p. parvus ( Lichtenstein, 1823 ): The nominate form occurs in the northern part of the African distribution area, from Senegal in the west to Ethiopia in the east, in South Sudan south to Juba . In addition, the birds in the southwest of the Arabian Peninsula correspond to the nominate form.
- C. p. laemostiga ( Reichenow , 1905 ): The birds of the lowlands of the coast of Mozambique and southern Somalia belong to this subspecies. They are smaller, darker in color and the mottled striped pattern on the throat is more noticeable than in the nominate form.
- C. p. myochrus ( Reichenow, 1886 ): This subspecies predominantly colonizes the higher altitudes in a strip extending from the south of Sudan via East Africa to South Africa. It is similar to C. p. laemostiga , but differs from this subspecies by a plumage that is clearly green.
- C. p. brachypterus ( Reichenow, 1903 ): This subspecies is found from Sierra Leone east to the northeast of the Democratic Republic of the Congo and south to Angola , and the palm swifts found on the islands in the Gulf of Guinea probably belong to this subspecies. The birds are darker than the nominate form and also as C. p. laemostiga . The pattern on the throat corresponds to the nominate form.
- C. p. hyphanes Brooke , 1972 : This subspecies colonizes the north of Namibia and Botswana , it is paler in color than the nominate form and has the most inconspicuous speckles on the throat.
- C. p. celer Clancey , 1983 : This subspecies occurs from Mozambique to Natal , the C. p. myochrus is similar in color, the shade is only slightly warmer. The mottled striped pattern of the throat is limited to the upper throat area. The birds are quite big.
- C. p. griveaudi Benson , 1960 : The subspecies occurring on the Comoros is extremely dark in color, the spotty pattern of the throat is very clear and extends into the upper area of the chest.
- C. p. gracilis ( Sharpe , 1871 ): This very small subspecies occurs in Madagascar . The color is darker than that of the subspecies of continental Africa, the spotty striped pattern of the throat is as clear as in C. p. griveaudi , but not up to the chest. The juveniles of this subspecies have a more clearly forked tail compared to the juveniles of the other subspecies.
literature
- Phil Chantler, Gerald Driessens: A Guide to the Swifts and Tree Swifts of the World . Pica Press, Mountfield 2000, ISBN 1-873403-83-6
- Joseph del Hoyo, Andrew Elliot and Jordi Sargatal (Eds.): Handbook of the Birds of the World. Volume 5: Barn-owls to Hummingbirds. Lynx Edicions, 1999, ISBN 84-87334-25-3 .
- James P. Chapin : The Birds of the Belgian Congo. Part II. In: Bulletin of the American Museum of Natural History. 75: 1-632, 1939
Individual evidence
- ↑ This and all information not specially marked are taken from the following source: Chantler, Driessens: A Guide to the Swifts and Tree Swifts of the World . Pp. 209ff, see literature
- ↑ del Hoyo et al .: Handbook of the birds of the world . P. 448, see literature
- ↑ Chapin: Birds of the Belgian Congo. P. 467, see literature
- ↑ del Hoyo et al .: Handbook of the birds of the world . P. 446, see literature
- ↑ Chantler, Driessens: A Guide to the Swifts and Tree Swifts of the World . P. 26, see literature
- ↑ BirdLife International: Species Factsheet - African Palm-swift ( Cypsiurus parvus ) . Retrieved October 12, 2009.
- ↑ JA Ledger: A review of Dennyus (Phthiraptera: Menoponidae) parasitic on the avian genera Apus and Cypsiurus. Journal of the Entomological Society of Southern Africa. 34: 37–56, 1971 ( online ( memento of the original from August 13, 2014 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this note. ).
- ↑ Chantler, Driessens: A Guide to the Swifts and Tree Swifts of the World. P. 25, see literature
Web links
- Cypsiurus parvus in the endangered Red List species the IUCN 2009. Posted by: BirdLife International, 2008. Accessed on 7 October of 2009.
- Sound recordings and videos for Cypsiurus parvus in the Macaulay Library of the Cornell Lab of Ornithology
