Grey-Headed Fish Eagle
A small to medium-sized bulky fish eagle. It 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. They have a body length of 61–75 cm. Females are heavier than males at 2.3–2.7 kg compared to 1.6 kg. The tail measures between 23–28 cm and the tarsus 8.5–10 cm. The wingspan measure between 155–170 cm. 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.
Breast and neck are brown, with the wings on top dark brown with blacker primaries and below brown. Juveniles the head and neck are brown, greyer on the ides of throat, with buff supercilia and whitish streaks. The rest of the upperparts are darker brown, edged with grey and secondaries and tertials faintly barred. Tail black and white marbled with broader dark subterminal band and white tip. Belly and thighs white, while breast and flanks brown streaked with white. Iris is darker than adult. As juveniles mature subterminal band becomes more prominent, head becomes greyer and loses streaking becoming uniformly brown
Habitat
The grey-headed fish eagle has a wide distribution that encompasses India and South-East Asia to Malaysia, Western Indonesia and Philippines. 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. It is uncommon in North and East Sri Lanka, rare and local in Nepal and uncommon and local in Bangladesh. It is rare and local in South Thailand and rare in Laos; scarce in Vietnam, Cambodia and Malaysia to Sumatra; very rare in Java and Sulawesi except for a small local population and scarce in Borneo and the Philippines.
Grey-headed fish eagles live in lowland forest up to 1,500 m above sea-level. 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. They are also known to frequent irrigation tanks in Sri Lanka, hence where their alternate English in Sri Lanka comes from.
Diet
As the common name suggests the grey-headed fish eagle is a specialist piscivore, which preys upon live fish and scavenges dead fish and occasionally reptiles and terrestrial birds and small mammals. 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. Also quarters over stretches of river or lakes and fish too heavy to lift may be dragged to bank to devour. It is also dynamic in prey pursuit and can catch fish in rough water such as rapids.
Breeding
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. 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. Breeding in the Prek Toal protected 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. 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. 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. 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. The clutch size can be between 2 and 4 eggs but usually 2 unmarked white eggs are laid per couple. 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.
Population
According to the IUCN Red List, they are classed as Near Threatened(NT). There population trend is decreasing. This species's global population is preliminarily estimated at 10,000-100,000 mature individuals on the basis that it may not exceed a five-figure total. This estimate equates to 15,000-150,000 individuals in total. A moderately rapid and on-going population decline is suspected on the basis of rates of habitat degradation and levels of pollution and over-fishing.
Threats
The most pertinent threats are the loss of undisturbed wetlands, over-fishing, siltation, pollution and persecution. There are also reports that this species may be deliberately targeted by poachers for meat. The construction of dams on the Mekong River has potential for the deposition of large amounts of mercury into the wetland area of Lake Tonle Sap as well as negative implications for the flood regime of the area and the Fish-eagle population there. The population at Lake Tonle Sap also appears to feed on water snakes and so the unsustainable harvest of water snakes may have a large impact on this species, at least at this locality.
Conservation
Conservation Actions Underway
Nesting surveys have taken place since 2005 at Prek Toal Ramsar Site.
Conservation Actions Proposed
Survey to reveal important areas and regularly monitor at various sites throughout its range. Protect forest in areas known to be important to the species. Conduct awareness campaigns involving local residents to engender pride in the species and encourage better care of wetland habitats.