Pacific sailors
| Pacific sailors | ||||||||||
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Nominal form of the Pacific sailor near Lake Baikal |
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Apus pacificus | ||||||||||
| ( Latham , 1802) |
The Pacific Swift ( Apus pacificus ) is the largest type of genus Apus in the family of sailors (Apodidae). With a body length of 17 to 18 centimeters, the species is a little larger than the similar common swift that is widespread and well-known in Europe . Like all sailors, Pacific sailors hunt for insects or arachnids in the air .
The Pacific sailor breeds in Eastern Asia . The populations in the north of the range are long-distance migrants and overwinter in Southeast Asia and Australia. The birds that breed further south only travel short distances or are sometimes resident birds .
description
Like swifts, Pacific swifts have slender bodies and long, sickle-shaped wings. These are a little longer than those of the common swift and although the wing shape is the same, the Pacific sailor looks sleeker. The head is slightly larger and more clearly separated from the trunk than that of the common swift, the tapering of the trunk is less.
The plumage is predominantly dark black-brown. The throat patch is large and triangular, but does not stand out very strongly from the underside, especially not when the plumage has been worn away. The black feathers on the underside have wide, white feather edges, which gives this part of the body a scaly appearance. What is striking is the white rump , which clearly stands out from the rest of the plumage and continues a little on the flanks, so that the white color can also be seen from the side. The tail is forked deep and very densely feathered, the outer edge of the fork appears wider than other sailors with forked tails.
Both sexes look the same, young birds hardly differ from young adults, only have a little white on the arm and inner hand wings .
The typical call is similar to that of the common swift , but softer and less whistling and sounds like "srieh".
Differentiation of similar species
The white rump and the strongly marked underside are the most important distinguishing features. Within its area of distribution, the Pacific sailor can easily be distinguished from all other normal colored sailors, because all others with a white rump differ significantly in shape and size. The closest is the Cape Swift , but its range does not overlap with that of the Pacific Swift. The Cape Swift is slimmer, the tail, in contrast to the Pacific Swift, tapers to a point when it is closed and when it is forked it shows only narrow edges.
In Europe , too, it is not always easy to identify a wandering Pacific sailor . A differentiation of partially albinotic individuals of the large species of the genus Apus can be difficult and require a close examination of the underside, since partially albinotic swifts, for example, can have a white rump similar to that of the Pacific swift.
Spreading and migrations
In the east of the Palearctic , the breeding area extends in the north from Siberia to Kamchatka and Japan , in the south to Annam , Vietnam , Thailand and Burma . The Pacific sailor also breeds on the islands of Taiwan , Hainan and Lan Yu , as well as probably in the Philippine province of Batanes . A geographically isolated population also breeds in the foothills of the Himalayas and the hills of Assam .
The occurrence of three different subspecies with different migration behavior in parts of Southeast Asia makes it difficult to determine the time of migration and the exact location of the winter quarters. The nominate form is a long-distance migrant that breeds in East Asia and overwinters in Indonesia , Melanesia and Australia . The populations of Siberia leave the breeding area from August to mid-September and return in May. The migration behavior of the isolated populations of the subspecies A. p. leuconyx in the foothills of the Himalayas and the hills of Assam has so far been poorly understood, the best interpretation is possibly classification as a resident bird with a tendency to migrate far across the entire Indian subcontinent. The A. p subspecies, which breed in Taiwan and southeastern Tibet . kanoi is a short-range migrant that has been observed overwintering in the Philippines, Indonesia, and Malaysia . The subspecies A. p. cooki is a resident .
habitat
Like the common swift, the Pacific swift occurs in a wide range of geographic and climatic zones, both in areas with a continental and those with a maritime climate , from the boreal zone in the north to the tropics in the south, both in the lowlands and at high altitudes . In summer it can be found at an altitude of 3800 meters in Nepal , while foraging for food it has been seen at altitudes above 4000 meters. He is regularly observed near human settlements. The winter quarters are mainly in lower elevations.
Reproduction
The beginning and end of the breeding season differ within the distribution area, the earliest period was found in Langtang in Nepal and ranges from March to May; breeding birds have been observed in Japan between June and August, which is the latest documented breeding period.
The Pacific sailor is a colony breeder. The nest is in the shape of a hemisphere, grass and other plant material is collected and stuck together with saliva. Nest locations can be found in niches in rock and mountain flanks as well as on buildings under roof overhangs. The nesting material is collected in flight and on the ground. In Nepal, the use of nest material from the Nepalese swallow ( Delichon nipalensis ) has been observed.
The clutch consists of one to three eggs which measure 24.0–27.5 × 16–17 millimeters in the nominate form; those of the subspecies A. p. leuconyx are significantly smaller. The incubation period is 17 days and the nestling period is around 40 days. Both sexes participate equally in the breeding business. At the Yellow Sea , where the conditions are certainly very favorable, about 74 percent of the laid eggs hatched, the escape rate was 64 percent, which results in an average of 1.24 young birds flown out per breeding pair per year.
behavior
The sociable Pacific sailors tend to be higher up in the air than most other sympathetic species of sailor. This is especially true in winter, when the Pacific sailors can only be found at lower altitudes during prolonged bad weather. They share these upper layers of air with some species of the genus Hirundapus , with which the Pacific sailor is often observed during the migration. Other sailors who hunt at similar heights are the Malay sailor and, with restrictions, the silver-humped sailor . In Malaysia , the average flight altitude of the Pacific sailor over a forested area was determined to be 185 meters.
In areas where it occurs sympathetically with the common swift - such as in Siberia - the Pacific sailor spends much longer than the common swift looking for food during twilight, occasionally until midnight.
Duration
The size of the distribution area is estimated at 10 million square kilometers, no information is available for the worldwide population and population trend, but there are signs of population growth. The Pacific sailor is quite common in the breeding area, but little detailed data is available. In a single large colony on an island in the Yellow Sea , a maximum of 8,000 individuals was recorded in 1985 after the breeding season.
Systematics
The Pacific sailor forms with the glossy-backed sailor a super-species within the genus Apus . David Lack even considered these two species to be con-specific in 1956 , but is alone with this view.
Four subspecies are distinguished for the Pacific sailor:
- A. p. pacificus: The nominate form breeds in the northern part of the range, its occurrence during migration in the range of other subspecies makes their identification difficult. The appearance corresponds to the description above , the variations in the rather large distribution area are small.
- A. p. kanoi: This subspecies occurs in Taiwan west to southeast Tibet, it is blacker than the nominate form, the throat spot and the area of the white coloration of the rump are smaller. The scaly structure of the underside is sometimes less noticeable, the tail fork is less deep. The size roughly corresponds to the nominate form.
- A. p. leuconyx: In the foothills of the Himalayas and the hills of Assam this breed is found isolated from the distribution area of the other subspecies. In the plumage color, A. p. leuconyx not significantly, but it is significantly smaller.
- A. p. cooki: This subspecies is found in Southeast Asia, south of the range of A. p. kanoi . The breed has the narrowest torso. The throat patch and the white rump stand out most clearly. A. p. cooki is a little smaller than the nominate form.
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
- David Lack : Swifts in a Tower . Chapman & Hall, London 1973, ISBN 0-412-12170-0
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 . Page 235 ff., See literature
- ↑ del Hoyo, Elliot, Sargatal (ed.): Handbook of the Birds of the World . Volume 5: Barn-Owls to Hummingbirds . Lynx Edicions, 1999, ISBN 84-87334-25-3
- ^ David Lack: The species of Apus . Ibis 98: 34-62
- ↑ Chantler, Driessens: A Guide to the Swifts and Tree Swifts of the World . Page 25 f., See literature
Web links
- Apus pacificus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed on 12 November, 2008.
- Feathers of the Pacific sailor
