River martin
Encyclopedia
The river martins form a distinctive subfamily Pseudochelidoninae within the swallow
and martin bird
family Hirundinidae. The two species are the African River Martin
Pseudochelidon eurystomina, found in the Congo
and Gabon
, and the White-eyed River Martin
Pseudochelidon sirintarae, known only from one site in Thailand. These are medium-sized, largely black swallows that have a light buoyant flight and feed on insects caught in the air. They appear to be more terrestrial than other swallows, frequently walking rather than perching, and the White-eyed may be crepuscular
. The African species excavates nest holes in sandy ridges in rivers, while the breeding locations and habits of the Asian bird are unknown.
When the African River Martin was first discovered in the 19th century, Gustav Hartlaub
thought it was a roller
, and later authors either placed it in its own family, or with the woodswallow
s. Study of the anatomy revealed that the species was closest to the swallows and martins, but that it possessed a number of distinctive features, such as its robust legs and feet and stout bill. These indicated that it should be placed in a separate subfamily. The two river martin species are usually considered to belong to a single genus, Pseudochelidon, due to their having a number of structural similarities. However, Brooke
proposed that the White-eyed River Martin be placed in a separate monotypic
genus Eurochelidon.
The African River Martin has a restricted distribution; it appears to be locally numerous, although its true status has not been fully investigated. The White-eyed River Martin was discovered as recently as 1969 and is only known from specimens and anecdotal evidence – no modern ornithologists have seen the species in the wild, and its breeding grounds are unknown. It may be extinct, although a possible sighting was reported in 2004.
was first formally described by German zoologist Gustav Hartlaub
in 1861, it was not initially identified as a member of the swallow and martin family. Hartlaub placed it with the roller
s, and later authors either put it in its own separate family, or with the woodswallow
s. It was only following study of the anatomy of the species by Lowe
that it was determined to be closely related to the swallows and martins, but sufficiently different to be placed in a separate subfamily Pseudochelidoninae.
The genus name Pseudochelidon comes from the Ancient Greek prefix ψευδο/pseudo, "false," and χελιδων/chelidôn, "swallow," reflecting its distinctiveness from the "true" swallows.
For many years the African River Martin was the sole member of its genus and subfamily until the discovery of the White-eyed River Martin, Pseudochelidon eurystomina, by Thai
ornithologist
Kitti Thonglongya
in 1968. Although some authorities follow Brooke
in placing that species in a separate genus Eurochelidon due to its significant differences from the African species, it remains a member of the same subfamily. Genetic studies confirmed that the two river martins form a distinct clade
from the typical swallows in the Hirundininae subfamily.
The river martins are in some ways intermediate between typical swallows and other passerine
s: they have stout bills, large feet and relatively strong legs, which is unusual in aerial feeders. They also have a large syrinx
(vocal organ) and a different bronchial
structure. The extent of their differences from other swallows and the wide geographical separation of these two martins suggest that they are relict populations of a group of species that diverged from the main swallow lineage early in its evolution
ary history, and they may be the most primitive of the swallows. Like other early hirundine lineages, they nest in burrows, rather than adopted nest holes or mud nests.
and Ubangi
rivers in the Democratic Republic of the Congo
. It is migratory
, wintering in coastal savannah in southern Gabon
and the Republic of Congo; it has recently been discovered to nest in beach ridges and grassland in its coastal wintering areas. The White-eyed River Martin is known only from its wintering site at Bueng Boraphet
lake in Thailand, where it was seen between the months of November and February. It may be migratory, but its breeding grounds and habitat are unknown, although river valleys in Northern Thailand or south-western China
are possibilities, as are Cambodia
and Myanmar
. However, doubts have been cast on whether it is actually migratory at all.
The African species' breeding habitat consists of forested rivers with islands with sandy shores for breeding. The nesting grounds of the White-eyed River Martin are unknown, but if the breeding habitat resembles that of its relative, it is likely to be the forested valleys of large rivers, which can provide sandbars and islands for nesting, and woodland over which the birds can catch insect prey. The African River Martin uses coastal savannah as its winter habitat. Based on its only known wintering site, the non-breeding habitat of the White-eyed is assumed to be in the vicinity of open fresh water for feeding, with reed-beds for the night-time roost.
in their respective ranges. Adults of both species have large, blue-glossed heads, a green tinge to the body plumage, and brown wings. The sexes are similar in plumage. The White-eyed has elongated outer tail feathers, a whitish rump, a white eye and eye-ring, and a yellow bill. The African has a red eye-ring and bill and lacks a contrasting rump patch or tail streamers. The juveniles of both species are similar to the adults, but with brown heads, and young White-eyeds lack the long tail streamers of the adults.
The African River Martin has a chee chee or cheer-cheer-cheer call when it is flying in flocks. It is very vocal during migration, giving harsh gull-like
calls, and appears to have a jingling courtship song. No calls have been described for the White-eyed River Martin.
Breeding behaviour is known only for the African River Martin. It nests in large colonies of up to 800 birds from December to April, when the river levels are low. Each pair excavates a 1–2 m (39.4–78.7 in) long tunnel in the exposed sandbanks. The pocket at the end of the tunnel has a few twigs and leaves to serve as a nest, onto which two to four unspotted white eggs are laid. It has chasing flight displays and will walk on the ground; it also displays on the ground, but the function of this is uncertain. It rarely perches during the breeding season. Although it has been assumed that the breeding habits of the White-eyed species resemble those of the African species, distinctive differences in foot and toe morphology suggest that it might not use a burrow for nesting.
The African River Martin feeds in flocks over river and forest, often far from water. It eats insect
s, mainly taking winged ant
s. The flight is strong and fast, interspersed with glides. Wintering birds regularly perch on treetops, wires and roofs. The White-eyed River Martin feeds on insect
s, including beetle
s, which are caught on the wing. Given its size and unusual mouth structure, it may take larger insects than other swallows. This species is described as graceful and buoyant in flight, and, like its African relative, appears reluctant to use perches. This behaviour, together with its unusual toe-shape and the fact that mud was found on the toes of one of the first specimens, suggests that this species may be relatively terrestrial. In winter, it roosts with Barn Swallow
s in reedbeds. Pamela C. Rasmussen
suggested that, given its unusually large eyes, the species might be nocturnal or crepuscular
, a factor that could make it highly cryptic
and thus partly explain how such a distinctive species remained undetected for so long. Although the fact that the first specimens were supposedly collected roosting at night in reed-beds might be a contraindication, it is possible that the birds might not actually have been caught at the roost; or they might be crepuscular, feeding at dawn and dusk; or they might be capable of both diurnal and nocturnal behaviour, depending on the season or local circumstances.
The White-eyed River Martin was seen in Thailand in 1972, 1977 and 1980, but not definitely since. There are unconfirmed sightings from Thailand in 1986 and Cambodia
in 2004. It is classified as critically endangered
by the International Union for the Conservation of Nature and Natural Resources (IUCN). This designation means that a species' numbers have decreased, or will decrease, by 80% within three generations. This species may be extinct, but the IUCN will not categorise it as such until extensive targeted surveys have been conducted. Despite legal protection under Appendix 1 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) agreement, it was captured by locals along with other swallow
s for sale as food or for release by devout Buddhists. Following its discovery by ornithogists, trappers were reported to have caught as many as 120 and sold them to the director of the Nakhon Sawan Fisheries Station who was unable to keep them alive in captivity. The small population may therefore have become non-viable.
One factor that reduces the chances of re-discovering the White-eyed Martin is the drastic decline in the numbers of swallows wintering at Beung Boraphet, its only known site, from the hundreds of thousands reported around 1970 to maximum counts of 8,000 made in the winter of 1980–1981. It is not certain whether this represents a real decline or a shift in site in response to persecution. Other potential causes for the species' decline include the disturbance of riverine sand bars, the construction of dams which flood the area upstream and alter the downstream hydrology, deforestation, and increasing conversion of its habitat to agriculture
. Very few swallows now roost in the Beung Boraphet reedbeds, preferring sugarcane
plantations, and, despite searching, the White-eyed River Martin has not been found in other nearby large swallow roosts. Beung Boraphet has been declared a Non-Hunting Area in an effort to protect the species, but surveys to find this martin have been unsuccessful. Past surveys include several at Beung Boraphet, a 1969 survey of the Nan Yom and Wang River
s of northern Thailand, and a 1996 survey of rivers in northern Laos
. A possible unverified sighting was reported in 2004.
The total population size of the African River Martin is unknown. In the late 1980s, it appeared to be common, if local, and large numbers were seen on migration in Gabon. However, it is particularly poorly known in the Democratic Republic of the Congo (DRC), and it is unclear if there is any relationship between the birds breeding in the DRC and those breeding in coastal areas of Gabon and the Republic of Congo. A flock of 15,000 birds was seen in 1997, and a mixed flock with Rosy Bee-eater
Merops malimbicus was estimated at 100,000 birds; nevertheless, due to the lack of detailed information, the species is classed by the IUCN as Data Deficient. In the 1950s, the species was caught and eaten in large quantities in the DRC by the local population, and this practice could be increasing. Breeding colonies in river sandbars are also liable to flooding, but thousands of birds were breeding on the grasslands east of Gamba as recently as 2005.
Swallow
The swallows and martins are a group of passerine birds in the family Hirundinidae which are characterised by their adaptation to aerial feeding...
and martin 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...
family Hirundinidae. The two species are the African River Martin
African River Martin
The African River Martin is a passerine bird, one of two members of the river martin subfamily of the swallow family Hirundinidae. It is a medium-sized, mainly black-plumaged species with red eyes, a broad orange-red bill and a square tail...
Pseudochelidon eurystomina, found in the Congo
Republic of the Congo
The Republic of the Congo , sometimes known locally as Congo-Brazzaville, is a state in Central Africa. It is bordered by Gabon, Cameroon, the Central African Republic, the Democratic Republic of the Congo , the Angolan exclave province of Cabinda, and the Gulf of Guinea.The region was dominated by...
and Gabon
Gabon
Gabon , officially the Gabonese Republic is a state in west central Africa sharing borders with Equatorial Guinea to the northwest, Cameroon to the north, and with the Republic of the Congo curving around the east and south. The Gulf of Guinea, an arm of the Atlantic Ocean is to the west...
, and the White-eyed River Martin
White-eyed River Martin
The White-eyed River Martin is a passerine bird, one of only two members of the river martin subfamily of the swallow family Hirundinidae...
Pseudochelidon sirintarae, known only from one site in Thailand. These are medium-sized, largely black swallows that have a light buoyant flight and feed on insects caught in the air. They appear to be more terrestrial than other swallows, frequently walking rather than perching, and the White-eyed may be crepuscular
Crepuscular
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...
. The African species excavates nest holes in sandy ridges in rivers, while the breeding locations and habits of the Asian bird are unknown.
When the African River Martin was first discovered in the 19th century, Gustav Hartlaub
Gustav Hartlaub
Karel Johan Gustav Hartlaub was a German physician and ornithologist.Hartlaub was born in Bremen, and studied at Bonn and Berlin before graduating in medicine at Göttingen. In 1840, he began to study and collect exotic birds, which he donated to the Bremen Natural History Museum. He described some...
thought it was a roller
Roller
The rollers are an Old World family, Coraciidae, of near passerine birds. The group gets its name from the aerial acrobatics some of these birds perform during courtship or territorial flights. Rollers resemble crows in size and build, and share the colourful appearance of kingfishers and...
, and later authors either placed it in its own family, or with the woodswallow
Woodswallow
Woodswallows are soft-plumaged, somber-coloured passerine birds. There is a single genus, Artamus, The woodswallows are either treated as a subfamily, Artaminae in an expanded family Artamidae, which includes the butcherbirds and Australian Magpie, or as the only genus in that family...
s. Study of the anatomy revealed that the species was closest to the swallows and martins, but that it possessed a number of distinctive features, such as its robust legs and feet and stout bill. These indicated that it should be placed in a separate subfamily. The two river martin species are usually considered to belong to a single genus, Pseudochelidon, due to their having a number of structural similarities. However, Brooke
Richard Kendall Brooke
Richard Kendall Brooke was a South African ornithologist.- Biography :Brooke was born in India where his father served in the British Army. His academic career began at Rhodes University in Grahamstown where he took a bachelor's degree in theology. Later he pursued a career as a minor civil...
proposed that the White-eyed River Martin be placed in a separate monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
genus Eurochelidon.
The African River Martin has a restricted distribution; it appears to be locally numerous, although its true status has not been fully investigated. The White-eyed River Martin was discovered as recently as 1969 and is only known from specimens and anecdotal evidence – no modern ornithologists have seen the species in the wild, and its breeding grounds are unknown. It may be extinct, although a possible sighting was reported in 2004.
Taxonomy
When a specimen of the African River Martin from GabonGabon
Gabon , officially the Gabonese Republic is a state in west central Africa sharing borders with Equatorial Guinea to the northwest, Cameroon to the north, and with the Republic of the Congo curving around the east and south. The Gulf of Guinea, an arm of the Atlantic Ocean is to the west...
was first formally described by German zoologist Gustav Hartlaub
Gustav Hartlaub
Karel Johan Gustav Hartlaub was a German physician and ornithologist.Hartlaub was born in Bremen, and studied at Bonn and Berlin before graduating in medicine at Göttingen. In 1840, he began to study and collect exotic birds, which he donated to the Bremen Natural History Museum. He described some...
in 1861, it was not initially identified as a member of the swallow and martin family. Hartlaub placed it with the roller
Roller
The rollers are an Old World family, Coraciidae, of near passerine birds. The group gets its name from the aerial acrobatics some of these birds perform during courtship or territorial flights. Rollers resemble crows in size and build, and share the colourful appearance of kingfishers and...
s, and later authors either put it in its own separate family, or with the woodswallow
Woodswallow
Woodswallows are soft-plumaged, somber-coloured passerine birds. There is a single genus, Artamus, The woodswallows are either treated as a subfamily, Artaminae in an expanded family Artamidae, which includes the butcherbirds and Australian Magpie, or as the only genus in that family...
s. It was only following study of the anatomy of the species by Lowe
Percy Lowe
Percy Roycroft Lowe was an English surgeon and ornithologist.Lowe was born at Stamford, Lincolnshire and studied medicine at Jesus College, Cambridge. He served as a civil surgeon in the Second Boer War, and it was whilst in South Africa that he became interested in ornithology...
that it was determined to be closely related to the swallows and martins, but sufficiently different to be placed in a separate subfamily Pseudochelidoninae.
The genus name Pseudochelidon comes from the Ancient Greek prefix ψευδο/pseudo, "false," and χελιδων/chelidôn, "swallow," reflecting its distinctiveness from the "true" swallows.
For many years the African River Martin was the sole member of its genus and subfamily until the discovery of the White-eyed River Martin, Pseudochelidon eurystomina, by Thai
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
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...
Kitti Thonglongya
Kitti Thonglongya
Kitti Thonglongya was an eminent Thai ornithologist and mammalogist. He is probably best known for two discoveries of endangered species.-Life:...
in 1968. Although some authorities follow Brooke
Richard Kendall Brooke
Richard Kendall Brooke was a South African ornithologist.- Biography :Brooke was born in India where his father served in the British Army. His academic career began at Rhodes University in Grahamstown where he took a bachelor's degree in theology. Later he pursued a career as a minor civil...
in placing that species in a separate genus Eurochelidon due to its significant differences from the African species, it remains a member of the same subfamily. Genetic studies confirmed that the two river martins form a distinct clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
from the typical swallows in the Hirundininae subfamily.
The river martins are in some ways intermediate between typical swallows and other passerine
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
s: they have stout bills, large feet and relatively strong legs, which is unusual in aerial feeders. They also have a large syrinx
Syrinx (biology)
Syrinx is the name for the vocal organ of birds. Located at the base of a bird's trachea, it produces sounds without the vocal cords of mammals. The sound is produced by vibrations of some or all of the membrana tympaniformis and the pessulus caused by air flowing through the syrinx...
(vocal organ) and a different bronchial
Bronchus
A bronchus is a passage of airway in the respiratory tract that conducts air into the lungs. The bronchus branches into smaller tubes, which in turn become bronchioles....
structure. The extent of their differences from other swallows and the wide geographical separation of these two martins suggest that they are relict populations of a group of species that diverged from the main swallow lineage early in its evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
ary history, and they may be the most primitive of the swallows. Like other early hirundine lineages, they nest in burrows, rather than adopted nest holes or mud nests.
Distribution and habitat
The two members of the family have geographically separate ranges. The African River Martin breeds along the CongoCongo River
The Congo River is a river in Africa, and is the deepest river in the world, with measured depths in excess of . It is the second largest river in the world by volume of water discharged, though it has only one-fifth the volume of the world's largest river, the Amazon...
and Ubangi
Ubangi River
The Ubangi River , also spelled Oubangui, is the largest right-bank tributary of the Congo River of Central Africa. It begins at the confluence of the Mbomou and Uele Rivers and flows west, then bends to the southwest and passes through Bangui, after which it flows south to the Congo at Liranga....
rivers in the Democratic Republic of the Congo
Democratic Republic of the Congo
The Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...
. It is migratory
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...
, wintering in coastal savannah in southern Gabon
Gabon
Gabon , officially the Gabonese Republic is a state in west central Africa sharing borders with Equatorial Guinea to the northwest, Cameroon to the north, and with the Republic of the Congo curving around the east and south. The Gulf of Guinea, an arm of the Atlantic Ocean is to the west...
and the Republic of Congo; it has recently been discovered to nest in beach ridges and grassland in its coastal wintering areas. The White-eyed River Martin is known only from its wintering site at Bueng Boraphet
Bueng Boraphet
Bueng Boraphet is the largest freshwater swamp and lake in central Thailand. It covers an area of 224 km² east of Nakhon Sawan, south of the Nan River close to its confluence with the Ping River....
lake in Thailand, where it was seen between the months of November and February. It may be migratory, but its breeding grounds and habitat are unknown, although river valleys in Northern Thailand or south-western China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
are possibilities, as are Cambodia
Cambodia
Cambodia , officially known as the Kingdom of Cambodia, is a country located in the southern portion of the Indochina Peninsula in Southeast Asia...
and Myanmar
Myanmar
Burma , officially the Republic of the Union of Myanmar , is a country in Southeast Asia. Burma is bordered by China on the northeast, Laos on the east, Thailand on the southeast, Bangladesh on the west, India on the northwest, the Bay of Bengal to the southwest, and the Andaman Sea on the south....
. However, doubts have been cast on whether it is actually migratory at all.
The African species' breeding habitat consists of forested rivers with islands with sandy shores for breeding. The nesting grounds of the White-eyed River Martin are unknown, but if the breeding habitat resembles that of its relative, it is likely to be the forested valleys of large rivers, which can provide sandbars and islands for nesting, and woodland over which the birds can catch insect prey. The African River Martin uses coastal savannah as its winter habitat. Based on its only known wintering site, the non-breeding habitat of the White-eyed is assumed to be in the vicinity of open fresh water for feeding, with reed-beds for the night-time roost.
Description
Both species are medium-sized (14–18 cm (5.5–7.1 in)), mainly black-plumaged swallows, unlikely to be confused with any other hirundineSwallow
The swallows and martins are a group of passerine birds in the family Hirundinidae which are characterised by their adaptation to aerial feeding...
in their respective ranges. Adults of both species have large, blue-glossed heads, a green tinge to the body plumage, and brown wings. The sexes are similar in plumage. The White-eyed has elongated outer tail feathers, a whitish rump, a white eye and eye-ring, and a yellow bill. The African has a red eye-ring and bill and lacks a contrasting rump patch or tail streamers. The juveniles of both species are similar to the adults, but with brown heads, and young White-eyeds lack the long tail streamers of the adults.
The African River Martin has a chee chee or cheer-cheer-cheer call when it is flying in flocks. It is very vocal during migration, giving harsh gull-like
Gull
Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...
calls, and appears to have a jingling courtship song. No calls have been described for the White-eyed River Martin.
Behaviour
The African River Martin feeds in flocks over river and forest, often far from water. It eats insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s, mainly taking winged ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s. The flight is strong and fast, interspersed with glides. Wintering birds regularly perch on treetops, wires and roofs. The White-eyed River Martin feeds on insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s, including beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, which are caught on the wing. Given its size and unusual mouth structure, it may take larger insects than other swallows. This species is described as graceful and buoyant in flight, and, like its African relative, appears reluctant to use perches. This behaviour, together with its unusual toe-shape and the fact that mud was found on the toes of one of the first specimens, suggests that this species may be relatively terrestrial. In winter, it roosts with Barn Swallow
Barn Swallow
The Barn Swallow is the most widespread species of swallow in the world. It is a distinctive passerine bird with blue upperparts, a long, deeply forked tail and curved, pointed wings. It is found in Europe, Asia, Africa and the Americas...
s in reedbeds. Pamela C. Rasmussen
Pamela C. Rasmussen
Professor Pamela Cecile Rasmussen is a prominent American ornithologist and expert on Asian birds. She was formerly a research associate at the Smithsonian Institution in Washington D.C., and is based at the Michigan State University...
suggested that, given its unusually large eyes, the species might be nocturnal or crepuscular
Crepuscular
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...
, a factor that could make it highly cryptic
Crypsis
In ecology, crypsis is the ability of an organism to avoid observation or detection by other organisms. It may be either a predation strategy or an antipredator adaptation, and methods include camouflage, nocturnality, subterranean lifestyle, transparency, and mimicry...
and thus partly explain how such a distinctive species remained undetected for so long. Although the fact that the first specimens were supposedly collected roosting at night in reed-beds might be a contraindication, it is possible that the birds might not actually have been caught at the roost; or they might be crepuscular, feeding at dawn and dusk; or they might be capable of both diurnal and nocturnal behaviour, depending on the season or local circumstances.
Status
Cambodia
Cambodia , officially known as the Kingdom of Cambodia, is a country located in the southern portion of the Indochina Peninsula in Southeast Asia...
in 2004. It is classified as critically endangered
Critically endangered
Version 2010.3 of the IUCN Red List of Threatened Species identified 3744 Critically Endangered species, subspecies and varieties, stocks and subpopulations.Critically Endangered by kingdom:*1993 Animalia*2 Fungi*1745 Plantae*4 Protista-References:...
by the International Union for the Conservation of Nature and Natural Resources (IUCN). This designation means that a species' numbers have decreased, or will decrease, by 80% within three generations. This species may be extinct, but the IUCN will not categorise it as such until extensive targeted surveys have been conducted. Despite legal protection under Appendix 1 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) agreement, it was captured by locals along with other swallow
Swallow
The swallows and martins are a group of passerine birds in the family Hirundinidae which are characterised by their adaptation to aerial feeding...
s for sale as food or for release by devout Buddhists. Following its discovery by ornithogists, trappers were reported to have caught as many as 120 and sold them to the director of the Nakhon Sawan Fisheries Station who was unable to keep them alive in captivity. The small population may therefore have become non-viable.
One factor that reduces the chances of re-discovering the White-eyed Martin is the drastic decline in the numbers of swallows wintering at Beung Boraphet, its only known site, from the hundreds of thousands reported around 1970 to maximum counts of 8,000 made in the winter of 1980–1981. It is not certain whether this represents a real decline or a shift in site in response to persecution. Other potential causes for the species' decline include the disturbance of riverine sand bars, the construction of dams which flood the area upstream and alter the downstream hydrology, deforestation, and increasing conversion of its habitat to agriculture
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
. Very few swallows now roost in the Beung Boraphet reedbeds, preferring sugarcane
Sugarcane
Sugarcane refers to any of six to 37 species of tall perennial grasses of the genus Saccharum . Native to the warm temperate to tropical regions of South Asia, they have stout, jointed, fibrous stalks that are rich in sugar, and measure two to six metres tall...
plantations, and, despite searching, the White-eyed River Martin has not been found in other nearby large swallow roosts. Beung Boraphet has been declared a Non-Hunting Area in an effort to protect the species, but surveys to find this martin have been unsuccessful. Past surveys include several at Beung Boraphet, a 1969 survey of the Nan Yom and Wang River
Wang River
The Wang River is a river in northern Thailand.-Geography:The Wang River is altogether 335nsnp;km long. Its waters flow from north to south. One of the principal settlements along the river is Lampang, which is situated on the north bank of a curve in the river. From Lampang, the river extends...
s of northern Thailand, and a 1996 survey of rivers in northern Laos
Laos
Laos Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ Sathalanalat Paxathipatai Paxaxon Lao, officially the Lao People's Democratic Republic, is a landlocked country in Southeast Asia, bordered by Burma and China to the northwest, Vietnam to the east, Cambodia to the south and Thailand to the west...
. A possible unverified sighting was reported in 2004.
The total population size of the African River Martin is unknown. In the late 1980s, it appeared to be common, if local, and large numbers were seen on migration in Gabon. However, it is particularly poorly known in the Democratic Republic of the Congo (DRC), and it is unclear if there is any relationship between the birds breeding in the DRC and those breeding in coastal areas of Gabon and the Republic of Congo. A flock of 15,000 birds was seen in 1997, and a mixed flock with Rosy Bee-eater
Rosy Bee-eater
The Rosy Bee-eater is a species of bird in the Meropidae family.It is found in Angola, Benin, Burkina Faso, Republic of the Congo, Democratic Republic of the Congo, Ivory Coast, Equatorial Guinea, Gabon, Ghana, Nigeria, and Togo....
Merops malimbicus was estimated at 100,000 birds; nevertheless, due to the lack of detailed information, the species is classed by the IUCN as Data Deficient. In the 1950s, the species was caught and eaten in large quantities in the DRC by the local population, and this practice could be increasing. Breeding colonies in river sandbars are also liable to flooding, but thousands of birds were breeding on the grasslands east of Gamba as recently as 2005.
External links
- African River Martin videos on the Internet Bird collection