Aerodramus
Encyclopedia
Aerodramus is a genus
of small, dark, cave-nesting bird
s in the Collocaliini
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 ornithologist
Harry Church Oberholser
in 1906.
This is a taxonomically difficult group of very similar species. Echolocation
, DNA sequencing
and parasitic 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 delicacy
'bird's nest soup
', the over-collection of which puts pressure on the swiftlet populations.
and the Indian Ocean
, with the greatest diversity in Southeast Asia
, Indonesia
and Papua New Guinea
. Several of the species are restricted to small islands, and their limited range can make them vulnerable, like the Seychelles
, Whitehead's
and Guam Swiftlet
s. The Mangaia Swiftlet
is a recently extinct species known only from fossils.
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.
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 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.
Aerodramus swiftlets are aerial insectivores, which take prey like 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.
Clutch size depends on the location and the food source, but generally Aerodramus swiftlets lay one or two eggs. 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.
Most Aerodramus swiftlets live in the tropical Indo-Pacific
region and do not 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
, Malaysian Borneo
.
Characteristics of behaviour, such as what materials apart from saliva the nests contain, can be used to differentiate between certain species of Aerodramus.
The genus Aerodramus is of special interest due to its use of 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 avian
species to use echolocation is the unrelated Oilbird
.
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.
The use of echolocation was once used to separate Aerodramus from the other non-echolocating cave swiftlet
genera Collocalia and 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.
It has recently been determined that the echolocation vocalizations do not agree with evolutionary relationship between swiftlet species as suggested by DNA
sequence comparison. This suggests that as in bat
s, echolocation sounds, once present, adapt rapidly and independently to the particular species' acoustic environment.
A study 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.
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. 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.
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.
can give information on relationships. A study of swiftlet parasites in northern Borneo involved transferring lice between closely related swiftlet species. 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.
and uses echolocation while active outside at night. It uses single, not double, clicks. 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 Swift
Hydrochous gigas, are sister taxa
, a relationship that would indicate paraphyly
of the genus Aerodramus.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of small, dark, cave-nesting bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s in the Collocaliini
Swiftlet
Swiftlets are birds contained within the four genera Aerodramus, Hydrochous, Schoutedenapus and Collocalia. They form the Collocaliini tribe within the swift family Apodidae. The group contains around thirty species mostly confined to southern Asia, south Pacific islands, and northeastern...
tribe
Tribe (biology)
In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...
of the swift
Swift
The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are actually not closely related to passerine species at all; swifts are in the separate order Apodiformes, which they share with hummingbirds...
family. Its members are confined to tropical and subtropical regions in southern Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, Oceania
Oceania
Oceania is a region centered on the islands of the tropical Pacific Ocean. Conceptions of what constitutes Oceania range from the coral atolls and volcanic islands of the South Pacific to the entire insular region between Asia and the Americas, including Australasia and the Malay Archipelago...
and northeastern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. Many of its members were formerly classified in Collocalia
Collocalia
Collocalia is a genus of swifts, containing some of the smaller species termed "swiftlets". Formerly a catch-all genus for these, a number of its erstwhile members are now normally placed in Aerodramus....
, but were first placed in a separate genus by American ornithologist
Ornithology
Ornithology is a branch of zoology that concerns the study of birds. Several aspects of ornithology differ from related disciplines, due partly to the high visibility and the aesthetic appeal of birds...
Harry Church Oberholser
Harry Church Oberholser
Harry Church Oberholser was an American ornithologist.Oberholser worked for the United States Bureau of Biological Survey from 1895 to 1941, first as an ornithologist, later as a biologist, and finally as an editor. He was the author of a number of books and articles...
in 1906.
This is a taxonomically difficult group of very similar species. Echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
, DNA sequencing
DNA sequencing
DNA sequencing includes several methods and technologies that are used for determining the order of the nucleotide bases—adenine, guanine, cytosine, and thymine—in a molecule of DNA....
and parasitic lice
Louse
Lice is the common name for over 3,000 species of wingless insects of the order Phthiraptera; three of which are classified as human disease agents...
have all been used to establish relationships, but some problems, such as the placement of the Papuan Swiftlet
Papuan Swiftlet
The Three-toed Swiftlet or Papuan Swiftlet is a species of swift.It is found in Indonesia and Papua New Guinea.-Source:* BirdLife International 2004. . Downloaded on 24 July 2007....
are not fully resolved. These swiftlets can pose major identification problems where several species occur.
What distinguishes Aerodramus swiftlet
Swiftlet
Swiftlets are birds contained within the four genera Aerodramus, Hydrochous, Schoutedenapus and Collocalia. They form the Collocaliini tribe within the swift family Apodidae. The group contains around thirty species mostly confined to southern Asia, south Pacific islands, and northeastern...
s from other swifts, and indeed almost all other bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
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
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
as a major component. In two species, saliva is the only material used, and the nests are collected for the famous Chinese delicacy
Chinese cuisine
Chinese cuisine is any of several styles originating in the regions of China, some of which have become highly popular in other parts of the world – from Asia to the Americas, Australia, Western Europe and Southern Africa...
'bird's nest soup
Bird's nest soup
Bird's nest soup is a delicacy in Chinese cuisine. A few species of swift, the cave swifts, are renowned for building the saliva nests used to produce the unique texture of this 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 AustraliaAustralia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
, with the greatest diversity in Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
, Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
and Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
. Several of the species are restricted to small islands, and their limited range can make them vulnerable, like the Seychelles
Seychelles Swiftlet
The Seychelles Swiftlet is a small bird of the swift family. It is found only in the Seychelles Islands in the Indian Ocean....
, Whitehead's
Whitehead's Swiftlet
The Whitehead's Swiftlet is a species of swift in the Apodidae family. It is endemic to the Philippines.Its natural habitat is subtropical or tropical moist montane forests. Its status is insufficiently known.-Source:...
and Guam Swiftlet
Guam Swiftlet
The Mariana Swiftlet or Guam Swiftlet, is a species of swift in the Apodidae family.It is found in Guam, Northern Mariana Islands, and the United States....
s. The Mangaia Swiftlet
Mangaia Swiftlet
The Mangaia Swiftlet is an extinct species of bird in the swift family. It became extinct during prehistoric times. It was endemic to Mangaia, Cook Islands...
is a recently extinct species known only from fossils.
Description
Flight feather
Flight feathers are the long, stiff, asymmetrically shaped, but symmetrically paired feathers on the wings or tail of a bird; those on the wings are called remiges while those on the tail are called rectrices . Their primary function is to aid in the generation of both thrust and lift, thereby...
s.
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 primary feathers
Flight feather
Flight feathers are the long, stiff, asymmetrically shaped, but symmetrically paired feathers on the wings or tail of a bird; those on the wings are called remiges while those on the tail are called rectrices . Their primary function is to aid in the generation of both thrust and lift, thereby...
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
Borneo
Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....
, New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
and the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, may not be separable in the field.
Behaviour
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
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.
Clutch size depends on the location and the food source, but generally Aerodramus swiftlets lay one or two eggs. 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.
Most Aerodramus swiftlets live in the tropical Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
region and do not migrate
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
. These birds usually remain in one cave or other roosting/nesting site. Examples of cave sites include the Niah Caves
Niah Caves
Niah Caves is located within the district of Miri in Sarawak, Malaysia. Part of Niah National Park, the main cave, Niah Great Cave, is located in Gunung Subis and is made up of several voluminous, high-ceilinged chambers...
and Gunung Mulu National Park
Gunung Mulu National Park
Gunung Mulu National Park near Miri, Sarawak, Malaysian Borneo, is a UNESCO World Heritage Site that encompasses incredible caves and karst formations in a mountainous equatorial rainforest setting...
, which are both located in Sarawak
Sarawak
Sarawak is one of two Malaysian states on the island of Borneo. Known as Bumi Kenyalang , Sarawak is situated on the north-west of the island. It is the largest state in Malaysia followed by Sabah, the second largest state located to the North- East.The administrative capital is Kuching, which...
, Malaysian Borneo
Borneo
Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....
.
Characteristics of behaviour, such as what materials apart from saliva the nests contain, can be used to differentiate between certain species of Aerodramus.
Echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
. The swiftlets use this technique to navigate in darkness through the chasms and shafts of the cave
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
s where they breed and roost at night. Apart from swiftlets, the only other avian
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
species to use echolocation is the unrelated Oilbird
Oilbird
The Oilbird , also known as Guácharo, is a bird found in the northern areas of South America . They are nocturnal feeders on the fruits of the Oil Palm and tropical laurels, and are the only nocturnal fruit eating birds in the world...
.
The Aerodramus swiftlets' echolocating double clicks are within the normal human hearing range and up to 3 millisecond
Millisecond
A millisecond is a thousandth of a second.10 milliseconds are called a centisecond....
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
Atiu Swiftlet
The Atiu Swiftlet is a species of bird in the swift family and endemic to Atiu in the Cook Islands.Its natural habitats are the islands fernlands and mixed horticultural areas over which it feeds and in makatea limestone caves within which it nests.-External links:*...
, Aerodramus sawtelli, and the Black-nest Swiftlet
Black-nest Swiftlet
The Black-nest Swiftlet is a species of swift in the Apodidae family.It is found in Brunei, Indonesia, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam....
, A. maximus, emit only single clicks. Interestingly, the former species also uses echolocation outside its caves.
The use of echolocation was once used to separate Aerodramus from the other non-echolocating cave swiftlet
Cave Swiftlet
The Cave Swiftlet is a species of swift in the Apodidae family.It is found in Indonesia and Malaysia.-References:* BirdLife International 2004. . Downloaded on 24 July 2007....
genera Collocalia and Hydrochous
Waterfall Swift
The Waterfall Swift , also known as the Giant Swiftlet, is a species of swift in the Apodidae family. It is monotypic within the genus Hydrochous. It is found in Indonesia and Malaysia. Its natural habitats are subtropical or tropical moist montanes and rivers. It is threatened by habitat loss....
(virtually nothing is known about Schoutedenapus
Schoutedenapus
Schoutedenapus is a genus of swift in the Apodidae family.It contains the following species:* Scarce Swift * Schouteden's Swift...
). However, recently, the Pygmy Swiftlet
Pygmy Swiftlet
The Pygmy Swiftlet is a species of swift in the Apodidae family.It is endemic to the Philippines.Its natural habitat is subtropical or tropical moist lowland forests. At under 9 cm , it the world's smallest swift....
, Collocalia troglodytes, was discovered making similar clicking noises both inside and outside its roosting cave.
It has recently been determined that the echolocation vocalizations do not agree with evolutionary relationship between swiftlet species as suggested by DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
sequence comparison. This suggests that as in bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s, echolocation sounds, once present, adapt rapidly and independently to the particular species' acoustic environment.
A study suggested that the echolocation subunits were mainly located in the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
, 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
Waterfall Swift
The Waterfall Swift , also known as the Giant Swiftlet, is a species of swift in the Apodidae family. It is monotypic within the genus Hydrochous. It is found in Indonesia and Malaysia. Its natural habitats are subtropical or tropical moist montanes and rivers. It is threatened by habitat loss....
let, Hydrochous gigas, which cannot echolocate, may be descended from an echolocating ancestor.
Saliva nests
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
nests of this swiftlet genus, which in some species contain no other material, are collected to make the delicacy bird's nest soup
Bird's nest soup
Bird's nest soup is a delicacy in Chinese cuisine. A few species of swift, the cave swifts, are renowned for building the saliva nests used to produce the unique texture of this soup....
. They therefore command extremely high prices.
Authentic bird's nest soup is made from the nests of the Edible-nest Swiftlet
Edible-nest Swiftlet
The Edible-nest Swiftlet is a small bird of the swift family which is found in South-east Asia. Its nest is made of solidified saliva and is used to make bird's nest soup.-Description:...
(or White-nest Swiftlet), Aerodramus fuciphagus, and the Black-nest Swiftlet
Black-nest Swiftlet
The Black-nest Swiftlet is a species of swift in the Apodidae family.It is found in Brunei, Indonesia, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam....
, 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. The Niah caves population of Black-nest Swiftlet
Black-nest Swiftlet
The Black-nest Swiftlet is a species of swift in the Apodidae family.It is found in Brunei, Indonesia, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam....
s plunged from around 1.5 million pairs in 1959 to 150,000–298,000 pairs in the early 1990s through over-harvesting.
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.
Lice
As with other taxonomically difficult groups, ectoparasitesParasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
can give information on relationships. A study of swiftlet parasites in northern Borneo involved transferring lice between closely related swiftlet species. 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 crepuscularCrepuscular
Crepuscular animals are those that are active primarily during twilight, that is during dawn and dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is, thus, in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright...
and uses echolocation while active outside at night. It uses single, not double, clicks. 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 Swift
Waterfall Swift
The Waterfall Swift , also known as the Giant Swiftlet, is a species of swift in the Apodidae family. It is monotypic within the genus Hydrochous. It is found in Indonesia and Malaysia. Its natural habitats are subtropical or tropical moist montanes and rivers. It is threatened by habitat loss....
Hydrochous gigas, are sister taxa
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
, a relationship that would indicate paraphyly
Paraphyly
A group of taxa is said to be paraphyletic if the group consists of all the descendants of a hypothetical closest common ancestor minus one or more monophyletic groups of descendants...
of the genus Aerodramus.
Species in taxonomic order
- Seychelles SwiftletSeychelles SwiftletThe Seychelles Swiftlet is a small bird of the swift family. It is found only in the Seychelles Islands in the Indian Ocean....
, Aerodramus elaphrus - Mascarene SwiftletMascarene SwiftletThe Mascarene Swiftlet is a species of swift in the Apodidae family.It is found in Mauritius and Réunion.Its natural habitats are subtropical or tropical moist lowland forests, subtropical or tropical high-altitude shrubland, subtropical or tropical high-altitude grassland, caves, arable land, and...
, Aerodramus francicus - Indian SwiftletIndian SwiftletThe Indian Swiftlet, or Indian Edible-nest Swiftlet, Aerodramus unicolor, is a small swift. It is a common resident colonial breeder in the hills of Sri Lanka and south west India.The half-cup nest is built on a vertical surface, often in a cave...
, Aerodramus unicolor - Philippine SwiftletPhilippine SwiftletThe Philippine Swiftlet is a species of swift in the Apodidae family. It is endemic to the Philippines.Its natural habitats are subtropical or tropical dry forests, subtropical or tropical moist lowland forests, and subtropical or tropical moist montane forests.-References:* BirdLife International...
, Aerodramus mearnsi - Moluccan SwiftletMoluccan SwiftletThe Moluccan Swiftlet is a species of swift in the Apodidae family.It is endemic to Indonesia.Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical moist montanes.-References:...
, Aerodramus infuscatus - Mountain SwiftletMountain SwiftletThe Mountain Swiftlet is a species of swift in the family Apodidae. It is endemic to the island of New Guinea and the nearby islands of Karkar, Yapen and Goodenough. It was once placed in the genus Collocalia but has been moved, with many others, to Aerodramus. The species is divided into three...
, Aerodramus hirundinaceus - White-rumped SwiftletWhite-rumped SwiftletThe White-rumped Swiftlet is a species of swift in the Apodidae family.It is found in American Samoa, Fiji, New Caledonia, Papua New Guinea, Samoa, Solomon Islands, Tonga, and Vanuatu...
, Aerodramus spodiopygius - Australian SwiftletAustralian SwiftletThe Australian Swiftlet is a small bird belonging to the genus Aerodramus in the swift family, Apodidae. It is endemic to Queensland in north-eastern Australia. It was formerly included in the White-rumped Swiftlet but is now commonly treated as a separate species...
, Aerodramus terraereginae - Himalayan SwiftletHimalayan SwiftletThe Himalayan Swiftlet, Aerodramus brevirostris, is a small swift. It is a common colonial breeder in the Himalayas and Southeast Asia. Some populations are migratory....
, Aerodramus brevirostris - Indochinese Swiftlet, Aerodramus rogersi (sometimes included in A. brevirostris)
- Volcano Swiftlet, Aerodramus vulcanorum (sometimes included in A. brevirostris)
- Whitehead's SwiftletWhitehead's SwiftletThe Whitehead's Swiftlet is a species of swift in the Apodidae family. It is endemic to the Philippines.Its natural habitat is subtropical or tropical moist montane forests. Its status is insufficiently known.-Source:...
, Aerodramus whiteheadi - Bare-legged SwiftletBare-legged SwiftletThe Bare-legged Swiftlet is a species of swift in the Apodidae family.It is found in Indonesia and Papua New Guinea.-References:* BirdLife International 2004. . Downloaded on 24 July 2007....
, Aerodramus nuditarsus - Mayr's SwiftletMayr's SwiftletThe Mayr's Swiftlet is a species of swift in the Apodidae family.It is found in Papua New Guinea and Solomon Islands.-Source:* BirdLife International 2004. . Downloaded on 24 July 2007....
, Aerodramus orientalis - Palawan SwiftletPalawan SwiftletThe Palawan Swiftlet is a species of swift in the Apodidae family. Some taxonomists consider it to be a subspecies of the Uniform Swiftlet. It is endemic to the Philippines....
, Aerodramus palawanensis - Mossy-nest SwiftletMossy-nest SwiftletThe Mossy-nest Swiftlet is a species of swift in the Apodidae family. Some taxonomists consider it to be a subspecies of the Uniform Swiftlet. It is found in northern Borneo, the Natuna and the Derawan Islands, islands off western Sumatra and Java...
, Aerodramus salangana (sometimes included in A. vanikorensis) - Uniform SwiftletUniform SwiftletThe Uniform Swiftlet, , also known as the Vanikoro or Lowland Swiftlet, is a gregarious, medium-sized swiftlet with a shallowly forked tail. The colouring is dark grey-brown, darker on the upperparts with somewhat paler underparts, especially on chin and throat...
, Aerodramus vanikorensis- Grey SwiftletGrey SwiftletThe Grey Swiftlet is usually considered a subspecies of the Uniform Swiftlet, although some taxonomists consider it a distinct species. It is endemic to the Philippines. Its natural habitat is subtropical or tropical moist lowland forests.-References:* BirdLife International 2004. . ...
, Aerodramus vanikorensis amelis
- Grey Swiftlet
- Palau SwiftletPalau SwiftletThe Palau Swiftlet is a species of swift in the Apodidae family.It is endemic to Palau.Its natural habitat is subtropical or tropical moist lowland forests.-References:...
, Aerodramus pelewensis - Mariana Swiftlet, Aerodramus bartschi
- Island SwiftletIsland SwiftletThe Island Swiftlet, also known as the Micronesian Swiftlet, or Caroline Islands Swiftlet, is a species of swift in the Apodidae family. Some taxonomists consider it to be a subspecies of the Uniform Swiftlet. It is endemic to the Caroline Islands...
, Aerodramus inquietus - Mangaia SwiftletMangaia SwiftletThe Mangaia Swiftlet is an extinct species of bird in the swift family. It became extinct during prehistoric times. It was endemic to Mangaia, Cook Islands...
, Aerodramus manuoi (prehistoric extinctionLate Quaternary prehistoric birdsPrehistoric birds are various taxa of birds that became extinct before recorded history, or more precisely, before they could be studied alive by bird scientists...
) - Atiu SwiftletAtiu SwiftletThe Atiu Swiftlet is a species of bird in the swift family and endemic to Atiu in the Cook Islands.Its natural habitats are the islands fernlands and mixed horticultural areas over which it feeds and in makatea limestone caves within which it nests.-External links:*...
, Aerodramus sawtelli - Tahiti SwiftletTahiti SwiftletThe Tahiti Swiftlet is a species of swift in the family Apodidae. It is endemic to the Society Islands in French Polynesia, where it occurs on Tahiti and Moorea. Its natural habitat is subtropical or tropical moist montanes.-References:* BirdLife International 2006. . Downloaded on 24...
, Aerodramus leucophaeus - Marquesan SwiftletMarquesan SwiftletThe Marquesan Swiftlet is a species of swift in the Apodidae family. It is endemic to French Polynesia. Its natural habitat is subtropical or tropical moist lowland forests.-References:...
, Aerodramus ocistus - Black-nest SwiftletBlack-nest SwiftletThe Black-nest Swiftlet is a species of swift in the Apodidae family.It is found in Brunei, Indonesia, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam....
, Aerodramus maximus - Edible-nest SwiftletEdible-nest SwiftletThe Edible-nest Swiftlet is a small bird of the swift family which is found in South-east Asia. Its nest is made of solidified saliva and is used to make bird's nest soup.-Description:...
, Aerodramus fuciphagus- Brown-rumped Swiftlet, Aerodramus (fuciphagus) vestitus
- German's SwiftletGerman's SwiftletThe German's Swiftlet is a species of swift.It is found in China, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam. Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical moist montanes.-Description:This swiftlet is...
, Aerodramus germani - Three-toed Swiftlet, Aerodramus papuensis