Aerodramus
490497
220722030
2008-06-21T07:04:40Z
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{{Taxobox
| name = ''Aerodramus''
| image = CollocaliaUnicolor.svg
|image_caption = Indian Swiftlet<br>''Aerodramus unicolor''
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[bird|Aves]]
| ordo = [[Apodiformes]]
| familia = [[swift|Apodidae]]
| genus = '''''Aerodramus'''''
| genus_authority = [[Harry Church Oberholser|Oberholser]], 1906
| subdivision_ranks = species
| subdivision =
''see text''
}}
'''''Aerodramus''''' is a [[genus]] of small, dark, cave-nesting [[bird]]s in the [[swiftlet|Collocaliini]] [[tribe (biology)|tribe]] of the [[swift]] family. Its members are confined to [[tropical]] and [[subtropical]] regions in southern [[Asia]], [[Oceania]] and northeastern [[Australia]]. Many of its members were formerly classified in ''[[Collocalia]]'', but were first placed in a separate genus by American [[ornithology|ornithologist]] [[Harry Church Oberholser]] in 1906.<ref name= ITIS>[http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=178017 ITIS standard report page for ''Aerodramus'']</ref>
This is a taxonomically difficult group of very similar species. [[Animal echolocation|Echolocation]], [[DNA sequencing]] and [[Parasite|parasitic]] [[louse|lice]] have all been used to establish relationships, but some problems, such as the placement of the [[Papuan Swiftlet]] are not fully resolved. These swiftlets can pose major identification problems where several species occur.
What distinguishes ''Aerodramus'' [[swiftlet]]s from other swifts, and indeed almost all other [[bird]]s, is their ability to use a simple but effective form of echolocation. This enables them to navigate within the breeding and roosting caves.
The nests of ''Aerodramus'' swiftlets are constructed with [[saliva]] as a major component. In two species, saliva is the only material used, and the nests are collected for the famous [[Chinese cuisine|Chinese delicacy]] '[[bird's nest soup]]', the over-collection of which puts pressure on the swiftlet populations.
==Distribution==
The range of these swiftlets is confined to tropical southern Asia, Oceania, northeastern [[Australia]] and the I[[Indian Ocean]], with the greatest diversity in [[Southeast Asia]], [[Indonesia]] and [[Papua New Guinea]].<ref name = Chantler/> Several of the species are restricted to small islands, and their limited range can make them vulnerable, like the [[Seychelles Swiftlet|Seychelles]], [[Whitehead's Swiftlet|Whitehead's]] and [[Guam Swiftlet]]s.<ref name = BirdLife1>[http://www.birdlife.org/datazone/sites/index.html?action=SpcHTMDetails.asp&sid=1710&m=0 Birdlife International species factsheet: ''Collocalia elaphra''.] Retrieved on 16 July /2007.</ref><ref name = BirdLife2> [http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=1721&m=0 Birdlife International species factsheet: ''Collocalia whiteheadi''.] Retrieved on 24 July 2007.</ref><ref name = BirdLife3> [http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=30057&m=0 Birdlife International species factsheet: ''Collocalia bartschi''.] Retrieved on 24 July 2007</ref> The [[Mangaia Swiftlet]] is a recently extinct species known only from fossils.<ref name = extinct>{{cite web|title= ''Aerodramus manuoi''|work= |url= http://www.extinct.minks-lang.de/7voegel/a.birdsarten.a-m/aerodramus.manuoi1.htm |publisher= |accessdate=2008-02-29}}</ref><ref name= Steadman >{{cite journal|last= Steadman |first= David W |coauthors= |month= July |year=2002 |title=A new species of swiftlet (Aves: Apodidae) from the late Quaternary of Mangaia, Cook Islands, Oceania |journal= Journal of Vertebrate Paleontology |volume= 22|issue=22|pages=326–331| doi = 10.1671/0272-4634(2002)022[0326:ANSOSA]2.0.CO;2 }}</ref>
==Description==
[[Image:Whiterumpedswiftlet.jpg|thumb|left|[[White-rumped Swiftlet]] in flight]]
''Aerodramus'' swiftlets are in many respects typical swifts, having narrow wings for fast flight, and a wide gape and small reduced beak surrounded by bristles for catching insects in flight. They have dull plumage which is mainly in shades of black, brown, and grey. Members of this genus typically have dark brown upper wings and upper body, sometimes with a paler rump, light brown underparts, a paler throat, and brownish-white under-wings with dark brown "armpits". Males and female plumages are similar in appearance, as is that of the juvenile, for those species for which it has been described; in some species the juvenile shows pale fringes to the [[flight feather]]s.<ref name=Chantler>Chantler, P. and Driessens, G. (2000). ''Swifts: a Guide to the Swifts and Treeswifts of the World'' Mountfield, East Sussex. Pica Press. ISBN 1-873403-83-6</ref>
The legs, as with many swifts, are very short, preventing the birds from perching, but allowing them to cling to vertical surfaces. The flight is mainly gliding due to very long [[flight feather|primary feathers]] and small breast muscles. ''Aerodramus'' swiftlets, depending on species, weigh 8–35 grammes (0.28–1.23 oz) and are 9–16 centimetres (0.28–1.23 in) long. These swiftlets are very similar, and where several species occur, such as [[Borneo]], [[New Guinea]] and the [[Philippines]], may not be separable in the field.<ref name=Chantler/>
==Behaviour==
[[Image:GermansSwiftlet 048.jpg|Juvenile [[German’s Swiftlet]]|thumb|right|These juvenile [[German's Swiftlet]]s have fallen from nests, and are being reared by hand.]]
''Aerodramus'' swiftlets are aerial insectivores, which take prey like [[fly|flies]] on the wing. They roost and breed in caves; during the day they leave the caves to forage for food, and return to roost at night. They are monogamous and both partners take part in caring for the nestlings. Males perform aerial displays to attract females and mating occurs at the nest. The breeding season overlaps the wet season, which corresponds to an increased insect population.<ref name=Chantler/>
Clutch size depends on the location and the food source, but generally ''Aerodramus'' swiftlets lay one or two eggs.<ref name=Chantler/> The eggs are a dull white, and are laid every other day. Many, if not all, species are colonial nesters; some build their nests in high, dark corners on cave walls.<ref name=Chantler/>
Most ''Aerodramus'' swiftlets live in the tropical [[Indo-Pacific]] region and do not [[bird migration|migrate]]. These birds usually remain in one cave or other roosting/nesting site. Examples of cave sites include the [[Niah Caves]] and [[Gunung Mulu National Park]], which are both located in [[Sarawak]], [[Malaysia]]n [[Borneo]].
Characteristics of behaviour, such as what materials apart from saliva the nests contain, can be used to differentiate between certain species of ''Aerodramus''.<ref name=Lee> Lee, P. L. M., Clayton, D. H., Griffiths, R., Page, R. D. M. (1996) "Does behavior reflect phylogeny in swiftlets (Aves: Apodidae)? A test using cytochrome ''b'' mitochondrial DNA sequences." ''Proc. natn. Acad. Sci. USA'' 93, pp. 7091–7096, July 1996 [http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=38941&blobtype=pdf Pdf retrieved 12 Nov 2007]</ref>
==Echolocation==
[[Image:Niah cave.jpg|[[Niah Caves|Niah cave]], a swiftlet nesting site|thumb|left]]
The genus ''Aerodramus'' is of special interest due to its use of [[Animal echolocation|echolocation]]. The swiftlets use this technique to navigate in darkness through the chasms and shafts of the [[cave]]s where they breed and roost at night. Apart from swiftlets, the only other [[bird|avian]] species to use echolocation is the unrelated [[Oilbird]].<ref name=ffrench>{{cite book| last = ffrench<!--this name should not be capitalized-->| first = Richard| title = A Guide to the Birds of Trinidad and Tobago| edition = 2nd edition| year = 1991| publisher = Comstock Publishing| isbn = 0-8014-9792-2}}</ref><ref name=Konishi>Konishi M., Knudsen E. I. (1979). "The oilbird: hearing and echolocation." ''Science'' 1979 Apr 27;204(4391):425-7 pmid: 441731 [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&list_uids=441731&cmd=Retrieve&indexed=google Abstract retrieved 12 Nov 2007]</ref>
The ''Aerodramus'' swiftlets' echolocating double clicks are within the normal human hearing range and up to 3 [[millisecond]]s apart, with the interval becoming shorter in darker locations. Unlike the rest of the genus (for those species which have been studied), the [[Atiu Swiftlet]], ''Aerodramus sawtelli'', and the [[Black-nest Swiftlet]], ''A. maximus'', emit only single clicks. Interestingly, the former species also uses echolocation outside its caves.<ref name = Fullard>Fullard, J.H., Barclay, R.M.R. and Thomas D.W. (1993) "Echolocation in free-flying Atiu Swiftlets (''Aerodramus sawtelli'')". ''Biotropica'' 25: 334–339. doi:10.2307/2388791 [http://links.jstor.org/sici?sici=0006-3606(199309)25%3A3%3C334%3AEIFAS(%3E2.0.CO%3B2-8 Abstract retrieved 12 Nov 2007]</ref>
The use of echolocation was once used to separate ''Aerodramus'' from the other non-echolocating [[cave swiftlet]] genera ''Collocalia'' and ''[[Waterfall Swift|Hydrochous]]'' (virtually nothing is known about ''[[Schoutedenapus]]''). However, recently, the [[Pygmy Swiftlet]], ''Collocalia troglodytes'', was discovered making similar clicking noises both inside and outside its roosting cave.<ref name=Price> Price, J. J., Johnson, K. P., Clayton, D. H. (2004). "The evolution of echolocation in swiftlets". ''Journal of Avian Biology'' 35 (2), 135–143. doi:10.1111/j.1474-919X.2005.00467.x [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1474-919X.2005.00467.x Abstract retrieved 12 Nov 2007]</ref>
It has recently been determined that the echolocation vocalizations do not agree with evolutionary relationship between swiftlet species as suggested by [[DNA]] sequence comparison.<ref name = Thomassen>Thomassen, H. A., and Povel, G. D. E. (2006). "Comparative and phylogenetic analysis of the echo clicks and social vocalizations of swiftlets (Aves: Apodidae)." ''Biological Journal of the Linnean Society'' 88 (4): 631–643. DOI: 10.1111/j.1095-8312.2006.00648.x [http://www.ingentaconnect.com/content/bsc/bij/2006/00000088/00000004/art00011;jsessionid=bpvvnse7qsh3.alice?format=print Abstract retrieved 12 Nov 2007]</ref> This suggests that as in [[bat]]s, echolocation sounds, once present, adapt rapidly and independently to the particular species' acoustic environment.
A study<ref name = Thomassen2>Thomassen, H. A., den Tex, R-J., de Bakker, M. A.G. and Povel, G. D. E. (2005) "Phylogenetic relationships amongst swifts and swiftlets: A multi locus approach." ''Molecular Phylogenetics and Evolution'' 37 (1): 264–277. doi:10.1016/j.ympev.2005.05.010 [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WNH-4GKW77V-1&_user=10&_coverDate=10%2F31%2F2005&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=db9ee62393f18c709c48ca09a0993e8f Abstract retrieved 12 Nov 2007]</ref> suggested that the echolocation subunits were mainly located in the [[central nervous system]], while the subunits in the vocal apparatus were already present and capable of use before echolocation even evolved. This study supports the hypothesis of independent evolution of echolocation in ''Aerodramus'' and ''Collocalia'', with the subsequent evolution of complex behaviour needed to complement the physical echolocation system, or just possibly that the vocal apparatus-parts of the echolocation system might even be inherited from some [[prehistoric]] [[nocturnal]] ancestor.
It has been suggested that the Giant or [[Waterfall Swift]]let, ''Hydrochous gigas'', which cannot echolocate, may be descended from an echolocating ancestor.<ref name=Chantler/>
==Saliva nests==
[[Image:SwiftletBirdNests.jpg|thumb|An edible nest]]
The intricately constructed [[saliva]] nests of this swiftlet genus, which in some species contain no other material, are collected to make the delicacy [[bird's nest soup]]. They therefore command extremely high prices.
Authentic bird's nest soup is made from the nests of the [[Edible-nest Swiftlet]] (or White-nest Swiftlet), ''Aerodramus fuciphagus'', and the [[Black-nest Swiftlet]], ''Aerodramus maximus''. Instead of incorporating twigs, feathers and straw like others in the genus, these two swiftlets make their nest only from strands of their gummy saliva, which harden when exposed to air. Once the nests are harvested, they are cleaned and sold to restaurants. Over the past twenty years, the high demand for the nests of these ''Aerodramus'' species has had an adverse effect on their populations.<ref name=Hobbs>Hobbs, J. J. (2004). "Problems in the harvest of edible birds’ nests in Sarawak and Sabah, Malaysian Borneo." ''Biodiversity and Conservation'' 13: 2209–2226. DOI: 10.1023/B:BIOC.0000047905.79709.7f [http://www.ingentaconnect.com/content/klu/bioc/2004/00000013/00000012/05147648 Abstract retrieved 12 Nov 2007]</ref><ref name=Marcone>Marcone, M. F. (2005). "Characterization of the edible bird's nest the ''Caviar of the East''." ''Food Research International'' 38:1125–1134. doi:10.1016/j.foodres.2005.02.008 [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T6V-4GHRBYJ-1&_user=10&_coverDate=12%2F31%2F2005&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=84ab2eeeba53cb499a10401f4d538cd9 Abstract retrieved 12 Nov 2007]</ref> The Niah caves population of [[Black-nest Swiftlet]]s plunged from around 1.5 million pairs in 1959 to 150,000–298,000 pairs in the early 1990s through over-harvesting.<ref name=Chantler/>
Early authors had doubts about the material used to make the nest, with whale and fish sperm and sea foam being proposed as the basis for construction. Even in the 1830s, when the use of saliva had been fairly well established, it was believed that it was only a cement to bind a sea plant which provided the bulk of the gelatinous material of the nest.<ref name=Rennie >{{cite book | last = Rennie | first = James | coauthors= |title = The Architecture of Birds | year = 1831| publisher = London: Charles Knight|pages 288–306| isbn = }}</ref>
==Lice==
As with other taxonomically difficult groups, [[parasitism|ectoparasites]] can give information on relationships.<ref name=Page>Page, R. D. M., Lee, P. L. M., Becher, S.A., Griffiths, R., Clayton D. H. (1997). "A Different Tempo of Evolution in Birds and their Parasitic Lice" [http://taxonomy.zoology.gla.ac.uk/rod/posters/swifts.html Text retrieved 12 Nov 2007]</ref> A study of swiftlet parasites in northern Borneo involved transferring lice between closely related swiftlet species.<ref name=Tompkins>Tompkins, D. M., Clayton D. H. (1999). "Host resources govern the specificity of swiftlet lice: size matters". ''Journal of Animal Ecology'' 68 (3), 489–500. doi:10.1046/j.1365-2656.1999.00297.x [http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-2656.1999.00297.x Abstract retrieved 12 Nov 2007]</ref> The survival of lice in most of these transfers was significantly reduced in proportion to the mean difference in feather barb size between the donor and recipient species of hosts. Thus, adaptation to a particular resource on the body of the host appears to govern the specificity of swiftlet lice. In transfers where lice survived, the lice moved to different areas on the body of the host where the mean barb diameter of the feathers on which the lice occurred had the required value.
==Papuan Swiftlet==
The Papuan Swiftlet, ''Aerodramus papuensis'', has three toes instead of the usual four in this group. It has the ability to echolocate, but whereas other previously studied species use echolocation primarily while flying in their caves, the Papuan Swiftlet appears to be nocturnal or [[crepuscular]] and uses echolocation while active outside at night. It uses single, not double, clicks.<ref name=Chantler/><ref name=Price2>Price J. J., Johnson, K. P., Bush, S. E., Clayton, D. H. (2004). "Phylogenetic relationships of the Papuan Swiftlet ''Aerodramus papuensis'' and implications for the evolution of avian echolocation". ''Ibis'', Volume 147, Number 4, October 2005, pp. 790–796(7) doi:10.1111/j.1474-919X.2005.00467.x.</ref> DNA sequence data provides strong support for a basal relationship between ''A. papuensis'' and other ''Aerodramus'' taxa and suggest that this species and the Waterfall Swiftlet, ''Hydrochous gigas'', are sister [[taxon|taxa]], a relationship that would indicate [[paraphyly]] of the genus ''Aerodramus''.<ref name=Price2/>
== Species in taxonomic order ==
[[Image:Esculent.jpg|thumb|[[John Latham]] figure of the "Esculent Swallow and its Nest"]]
* [[Seychelles Swiftlet]], ''Aerodramus elaphrus''
* [[Mascarene Swiftlet]], ''Aerodramus francicus''
* [[Indian Swiftlet]], ''Aerodramus unicolor''
* [[Philippine Swiftlet]], ''Aerodramus mearnsi''
* [[Moluccan Swiftlet]], ''Aerodramus infuscatus''
* [[Mountain Swiftlet]], ''Aerodramus hirundinaceus''
* [[White-rumped Swiftlet]], ''Aerodramus spodiopygius''
* [[Australian Swiftlet]], ''Aerodramus terraereginae''
* [[Himalayan Swiftlet]], ''Aerodramus brevirostris''
* [[Indochinese Swiftlet]], ''Aerodramus rogersi'' Sometimes considered to be a [[subspecies]] of ''A. brevirostris''
* [[Volcano Swiftlet]], ''Aerodramus vulcanorum'' Sometimes considered to be a subspecies of ''A. brevirostris''
* [[Whitehead's Swiftlet]], ''Aerodramus whiteheadi''
* [[Bare-legged Swiftlet]], ''Aerodramus nuditarsus''
* [[Mayr's Swiftlet]], ''Aerodramus orientalis''
* [[Palawan Swiftlet]], ''Aerodramus palawanensis''
* [[Mossy-nest Swiftlet]], ''Aerodramus salangana'' Sometimes considered to be a subspecies of ''A. vanikorensis''
* [[Uniform Swiftlet]], ''Aerodramus vanikorensis''
* [[Grey Swiftlet]], ''Aerodramus amelis''
* [[Palau Swiftlet]], ''Aerodramus pelewensis''
* [[Guam Swiftlet]], ''Aerodramus bartschi''
* [[Caroline Islands Swiftlet]], ''Aerodramus inquietus''
* [[Mangaia Swiftlet]], ''Aerodramus manuoi'' ([[Late Quaternary prehistoric birds|prehistoric extinction]])
* [[Atiu Swiftlet]], ''Aerodramus sawtelli''
* [[Tahiti Swiftlet|Polynesian Swiftlet]], ''Aerodramus leucophaeus''
* [[Marquesan Swiftlet]], ''Aerodramus ocistus''
* [[Black-nest Swiftlet]], ''Aerodramus maximus''
* [[Edible-nest Swiftlet]], ''Aerodramus fuciphagus'' The subspecies ''vestitus'' is sometimes separated as the [[Brown-rumped Swiftlet]]
* [[German's Swiftlet]], ''Aerodramus germani''
* [[Papuan Swiftlet]], ''Aerodramus papuensis'' Probably should be moved to a distinct genus
==References==<!-- JSystPaleontol5:1. RecAustrMus57:179. -->
{{reflist}}
[[Category:Aerodramus]]
[[Category:Genera of birds]]
[[Category:Cave birds]]
[[eo:Erodramo]]