Grey-headed fish eagle | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Accipitriformes |
Family: | Accipitridae |
Genus: | Icthyophaga |
Species: | I. ichthyaetus |
Binomial name | |
Icthyophaga ichthyaetus (Horsfield, 1821) | |
Synonyms | |
|
The grey-headed fish eagle (Icthyophaga ichthyaetus) is a fish-eating bird of prey from Southeast Asia. [2] It is a large stocky raptor with adults having dark brown upper body, grey head and lighter underbelly and white legs. [3] Juveniles are paler with darker streaking. It is often confused with the lesser fish eagle (Icthyophaga humilis) and the Pallas's fish eagle. The lesser fish eagle is similar in plumage but smaller and the Pallas's fish eagle shares the same habitat and feeding behaviour but is larger with longer wings and darker underparts. Is often called tank eagle in Sri Lanka due to its fondness for irrigation tanks. [4]
The grey-headed fish eagle is included in the order Accipitriformes and the family Accipitridae, which includes most birds of prey except for the ospreys and falcons. [4] Lerner & Mindell placed the grey-headed fish eagle in the subfamily Haliaeetinae, which includes the genera Haliaeetus (sea eagles) [5] It was first described by Horsfield in 1841 as Falco ichthyaetus. [6] This paraphyletic group forms a close sister relationship with the subfamily Milvinae (composed of two genera, Milvus and Haliatur), based on the shared trait of basal fusion of the second and third phalanges found only in these two groups. [7] Some taxonomic authorities place this species in the monotypic genus Ichthyophaga.
A smallish to medium-sized but quite bulky fish eagle. Has a small bill, a small head on long neck, rounded tail and shortish legs with unfeathered tarsi and long talons. Wings aren't very long and wingtips reach less than halfway down tail. Males and females are sexually dimorphic. The grey-headed fish eagle has a body length of 61–75 cm. [6] Females are heavier than males at 2.3–2.7 kg compared to 1.6 kg. [4] The tail measures between 23–28 cm and the tarsus 8.5–10 cm. [4] The wingspan measure between 155–170 cm. [6]
Adults are grey-brown with a pale grey head and pale iris, belly and tail are white with the having a broad black subterminal band. [3] Breast and neck are brown, with the wings on top dark brown with blacker primaries and below brown. [4] Juveniles the head and neck are brown, greyer on the ides of throat, with buff supercilia and whitish streaks. [4] The rest of the upperparts are darker brown, edged with grey and secondaries and tertials faintly barred. [3] [4] Tail black and white marbled with broader dark subterminal band and white tip. [3] Belly and thighs white, while breast and flanks brown streaked with white. [4] Iris is darker than adult. [3] As juveniles mature subterminal band becomes more prominent, head becomes greyer and loses streaking becoming uniformly brown. [4]
The grey-headed fish eagle has a wide distribution (38˚ N to 6˚ S) that encompasses India and South-East Asia to Malaysia, Western Indonesia and Philippines. [4] It is generally uncommon but can be rare or local. In North and East India it is found in Rajasthan, Uttar Pradesh, Bihar and Assam. [4] It is uncommon in North and East Sri Lanka, [4] rare and local in Nepal and uncommon and local in Bangladesh. [3] It is rare and local in South Thailand and rare in Laos; [4] scarce in Vietnam, Cambodia and Malaysia to Sumatra; [8] [9] [10] very rare in Java and Sulawesi except for a small local population and scarce in Borneo and the Philippines. [4] [11]
Grey-headed fish eagles live in lowland forest up to 1,500 m above sea-level. [4] Their nests are close to bodies of water such as slow-moving rivers and streams, lakes, lagoons, reservoirs, marshes, swamps and coastal lagoons and estuaries. [4] [9] They are also known to frequent irrigation tanks in Sri Lanka, hence where their alternate English in Sri Lanka comes from. [3]
It is a sedentary bird that can be solitary or occur in pairs. It is non-migratory. Juveniles disperse from the breeding areas, presumably in search of mates or another food source. The grey headed fish eagle spends much of its time perching upright on bare branches over water bodies, occasionally flying down to catch fish. [4] Flight is heavy looking with sharp and full wing-beats on flattish wings. [4] Spends little time in the air soaring possibly due to habitat it lives in and no other aerial displays have been described.
The breeding season of the grey-headed fish eagle usually takes place between November and May across most of its mainland range, but changes from December to March in Sri Lanka, November to January in India. [4] Nests have been found in January–March in Burma, April in Sumatra and August in Borneo, it is unclear whether these nest were old or being used for breeding. [6] Breeding in the protected Prek Toal area of the Tonlé Sap follow the flood regimes that begin in September, with eggs near hatching or hatching at peak flood waters in October–November. [9]
The grey-headed fish eagle builds a huge stick nest, up to 1.5 metres across and, with repeated use, up to 2 metres deep. [4] The nest is lined with green leaves and were situated in tall trees (8–30 m) on or near the top of the tree with an open crown structure, which can be in a forest or a standalone tree. [4] [10] Nest sites were always near or by a water source with the avoidance of human habitations and is consistent with other fish eagles due to ease of access and food abundance. [10]
The clutch size can be between 2 and 4 eggs but usually 2 unmarked white eggs are laid per couple. [4] Little is known about the level of parental care employed by the grey headed fish eagle, the evidence points towards monogamy and shared parental care duties. Both incubation, foraging and fledgling feeding are carried out by the male and female, with incubation lasting 45–50 days and the fledgling period 70 days. [4] [10]
As the common name suggests the grey-headed fish eagle is a specialist piscivore, which preys upon live fish and scavenges dead fish [9] and occasionally reptiles and terrestrial birds and small mammals. [4] Tingay et al. [9] found that the diet of the grey-headed fish eagle in the Prek Toal protected area of the Tonlé Sap contains the endangered Tonlé Sap water snake. Whether this is the primary prey item of their diet or a seasonal occurrence in this are remains unclear. The most common method of foraging used is to catch fish from a hunting perch close to a water source with a short flight to snatch prey on the water surface or just below. [6] Also quarters over stretches of river or lakes and fish too heavy to lift may be dragged to bank to devour. [4] It is also dynamic in prey pursuit and can catch fish in rough water such as rapids. [3] Both species in the genus Ichthyophaga have strongly recurved talons like the osprey (Pandionidae) a specialisation for catching fish, which is lacking in the genus Haliaeetus (sea eagles). [12]
The calls of the grey-headed fish eagle include a gurgling awh-awhr and chee-warr repeated 5–6 times, an owlish ooo-wok, ooo-wok, ooo-wok, a nasally honking uh-wuk and a loud high pitched scream. [3] [4] These begin as subdued low short notes each succeeding one more strongly upturned and more strident then previous then dying away again and are uttered from a perch or on the wing. [3] [4] Fledglings give a longer nasal uuuw-whaar that starts low and subdued then becomes, louder and higher and strident. [3] During the breeding season becomes quite vocal, with calls being loud and far carrying, often calling also at night. [4]
Although not currently considered to be threatened with extinction, the population of grey-headed fish eagles is declining, the result of numerous and varied threats. The loss of suitable wetland habitat, deforestation, over-fishing, siltation, persecution, human disturbance and pollution resulting in a loss of nesting sites and reduced food supply. [1] [4] Tingay et al. [9] [10] noted that these statements are based mostly on anecdotal evidence, although their studies found a definitive negative link between human habitation and grey-headed fish eagle nest occupancy rates in Cambodia. Another critical threat to the Cambodian populations of the grey-headed fish eagle on the Tonlé Sap is the damming of the Mekong River for hydropower, which will possibly have adverse effects on critical flood regimes of the Tonlé Sap. [9] [10]
The grey-headed fish eagle is currently listed as Near-Threatened on the IUCN Red List. [1] The population is estimated to be between 10,000–100,000 mature individuals on the basis that it may not exceed a five figure total. [1] This estimate was completed in 2001 with poor data quality, combined with a marked decrease in populations is would be reasonable to assume that the number is closer to 10,000 and bordering on being classified Vulnerable. [1] The population is spread out over 5 million km² and is now thought be only common locally, with moderate rapid population decline throughout its range. [1]
Although there are no active conservation measures currently in place for the grey-headed fish eagle, there is an annual monitoring programme for the breeding population in the Prek Toal protected area at the Tonlé Sap Lake in Cambodia, which has been conducted each year since 2006. [9] The programme provides baseline information on the ecology of the species and the status and distribution of the breeding population. [10] A number of other conservation actions have also been proposed by the IUCN, these include surveys to reveal important areas and regularly monitor at various sites throughout its range, protect forest in areas known to be important to the species and conduct awareness campaigns involving local residents to engender pride in the species and encourage better care of wetland areas. [1]
The bald eagle is a bird of prey found in North America. A sea eagle, it has two known subspecies and forms a species pair with the white-tailed eagle, which occupies the same niche as the bald eagle in the Palearctic. Its range includes most of Canada and Alaska, all of the contiguous United States, and northern Mexico. It is found near large bodies of open water with an abundant food supply and old-growth trees for nesting.
Eagle is the common name for the golden eagle, bald eagle, and other birds of prey in the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. True eagles comprise the genus Aquila. Most of the 68 species of eagles are from Eurasia and Africa. Outside this area, just 14 species can be found—two in North America, nine in Central and South America, and three in Australia.
The Accipitridae is one of the three families within the order Accipitriformes, and is a family of small to large birds of prey with strongly hooked bills and variable morphology based on diet. They feed on a range of prey items from insects to medium-sized mammals, with a number feeding on carrion and a few feeding on fruit. The Accipitridae have a cosmopolitan distribution, being found on all the world's continents and a number of oceanic island groups. Some species are migratory. The family contains 255 species which are divided into 70 genera.
The white-tailed eagle, sometimes known as the 'sea eagle', is a large bird of prey, widely distributed across temperate Eurasia. Like all eagles, it is a member of the family Accipitridae which includes other diurnal raptors such as hawks, kites, and harriers. One of up to eleven members in the genus Haliaeetus, which are commonly called sea eagles, it is also referred to as the white-tailed sea-eagle. Sometimes, it is known as the ern or erne, gray sea eagle and Eurasian sea eagle.
The white-bellied sea eagle, also known as the white-breasted sea eagle, is a large diurnal bird of prey in the family Accipitridae. Originally described by Johann Friedrich Gmelin in 1788, it is closely related to Sanford's sea eagle of the Solomon Islands, and the two are considered a superspecies. A distinctive bird, the adult white-bellied sea eagle has a white head, breast, under-wing coverts and tail. The upper parts are grey and the black under-wing flight feathers contrast with the white coverts. The tail is short and wedge-shaped as in all Haliaeetinae species. Like many raptors, the female is larger than the male, and can measure up to 90 cm (35 in) long with a wingspan of up to 2.2 m (7.2 ft), and weigh 4.5 kg (9.9 lb). Immature birds have brown plumage, which is gradually replaced by white until the age of five or six years. The call is a loud goose-like honking.
The lizard buzzard, or lizard hawk, is a bird of prey in the family Accipitridae. It is native to Sub-Saharan Africa. Despite its name, it may be more closely related to the Accipiter hawks than the Buteo buzzards.
The mountain hawk-eagle or Hodgson's hawk-eagle, is a large bird of prey native to Asia. The latter name is in reference to the naturalist, Brian Houghton Hodgson, who described the species after collecting one himself in the Himalayas. A less widely recognized common English name is the feather-toed eagle. Like all eagles, it is in the family Accipitridae. Its feathered tarsus marks this species as a member of the subfamily Aquilinae. It is a confirmed breeding species in the northern part of the Indian subcontinent, from India, Nepal through Bangladesh to Thailand, Taiwan, Vietnam and Japan, although its distribution could be wider still as breeding species. Like other Asian hawk-eagles, this species was earlier treated under the genera of Spizaetus but genetic studies have shown this group to be paraphyletic, resulting in the Old World members being placed in Nisaetus and separated from the New World species. As is typical of hawk-eagles, the mountain hawk-eagle is a forest dwelling opportunistic predator who readily varies its prey selection between birds, mammals and reptiles along with other vertebrates. Although classified currently as a least-concern species due its persistence over a rather wide distribution, this species is often quite rare and scarce and seems to be decreasing, especially in response to large-scale habitat degradation and deforestation.
Icthyophaga or Ichthyophaga is a genus of six species of eagles, closely related to the sea eagles in the genus Haliaeetus. In fact, some taxonomic authorities place this genus within Haliaeetus. Both are native to southeastern Asia, from the Indian subcontinent southeast to Sulawesi. They are smaller than the Haliaeetus eagles, though overlapping in size with the smaller species of that genus. They share similar plumage, with grey heads grading into dull grey-brown wings and bodies, and white belly and legs. They differ in tail colour, with the lesser fish eagle having a brown tail, and the grey-headed fish eagle having a white tail with a black terminal band, and also in size, with the lesser fish eagle only about half of the weight of the grey-headed fish eagle.
The Madagascar fish eagle or Madagascar sea-eagle, is a large bird of prey in the family Accipitridae which also includes many other diurnal raptors such as kites, buzzards and harriers. It is endemic to the coastal strip in the northwest of Madagascar. It is about 63 cm (25 in) long and has a pale brown head, dark brown body and white tail. The Madagascar fish eagle has been suffering from a declining population and is threatened by habitat destruction and persecution, and the International Union for Conservation of Nature has rated its conservation status as being "critically endangered".
The milky stork is a stork species inhabiting predominantly mangroves in Southeast Asia. It is native to Cambodia, Vietnam, Malaysia and Indonesia. It is currently included in the genus Mycteria, is around 91–97 cm (36–38 in) tall, with a wingspan of 43.5–50 cm (17.1–19.7 in) and a tail around 14.5–17 cm (5.7–6.7 in). Its plumage is white apart from a few feathers at the wings and tail. Since the 1980's, the global milky stork population has declined from 5,000 to 2,000 individuals due to habitat destruction, overfishing and illegal smuggling of chicks. It is listed as Endangered on the IUCN Red List.
Steller's sea eagle, also known as Pacific sea eagle or white-shouldered eagle, is a very large diurnal bird of prey in the family Accipitridae. It was described first by Peter Simon Pallas in 1811. No subspecies are recognised. A sturdy eagle, it has dark brown plumage with white wings and tail, a yellow beak, and yellow talons. Typically, it is the heaviest eagle in the world, at about 5 to 10 kg, but in some standard measurements, may be ranked below the harpy eagle and the Philippine eagle. Steller's sea eagle females are bigger than males.
The bateleur, also known as the bateleur eagle, is a medium-sized eagle in the family Accipitridae. It is often considered a relative of the snake eagles and, like them, it is classified within the subfamily Circaetinae. It is the only member of the genus Terathopius and may be the origin of the "Zimbabwe Bird", the national emblem of Zimbabwe. Adult bateleurs are generally black in colour with a chestnut colour on the mantle as well as also on the rump and tail. Adults also have gray patches about the leading edges of the wings with bright red on their cere and their feet. Adults also show white greater coverts, contrasting with black remiges in males, gray patches on the underwing primaries and black wingtips. The juvenile bateleur is quite different, being largely drab brown with a bit of paler feather scaling. All bateleurs have extremely large heads for their size, rather small bills, large feet, relatively short legs, long, bow-like wings and uniquely short tails, which are much smaller still on adults compared to juvenile birds.
The lesser fish eagle is a species of Icthyophaga found in the Indian subcontinent, primarily in the foothills of the Himalayas, and south-east Asia. There are records from Gujarat, Central India and in more recent times from the Kaveri river valley in southern India, although the south Indian records are now thought to come from an isolated population, disjunct from the species' normal range. Some taxonomic authorities place this species in the monotypic genus Icthyophaga. Others place it in the genus Haliaeetus.
Sanford's sea eagle, also known as Sanford's fish eagle or the Solomon eagle, is a sea eagle endemic to the Solomon Islands archipelago.
The little eagle is a very small eagle endemic to Australia.
The grey-bellied hawk or grey-bellied goshawk is a fairly large and rare species of forest-dwelling South American bird of prey in the family Accipitridae.
The Tonlé Sap Biosphere Reserve is a unique ecological phenomenon surrounding the Tonlé Sap or Great Lake of Cambodia. In 1997, it was successfully nominated as a UNESCO Biosphere Reserve.
Stung Sen is a protected multiple use management area and wildlife sanctuary in the Kampong Thom Province of Cambodia. It is located near the south-eastern tip of the Tonlé Sap, one of three wildlife sanctuaries around the lake, including Boeng Tonlé Chhmar and Prek Toal.
The eastern osprey is a diurnal, fish-eating bird of prey. They live in Oceania at coastal regions of the Australian continent, the Indonesian islands, New Guinea, and the Philippines. It is usually sedentary and pairs breed at the same nest site, building up a substantial structure on dead trees or limbs. The subspecies resides in a habitat close to coasts and estuaries that provide opportunities for fishing. In 2022, it was considered a defunct species by the IOC, due to its low genetic divergences and absence in morphological differences. The eastern osprey's diet consists mostly of vertebrate fish species. It possesses specialised physical characteristics and exhibits unique behaviour to assist in hunting and catching prey.
Diospyros cambodiana is a tree in the Ebenaceae family, endemic to the Mekong basin, Cambodia. It grows some 15-20m tall in flooded/swamp forest. One of its vernacular names derives from the perceived likeness of its flowers to mouse droppings. The plant is used for construction, craftwork, firewood and medicine.