Data Zone
Justification of Red List category
Icthyophaga ichthyaetus is classified as Near Threatened under A2cd+3cd+4cd. Although it has a large range the species is patchily distributed, and is suffering suspected population reductions of 20-29% over three generations, driven by a combination of habitat degradation and hunting.
Population justification
There is little information on the population size of I. ichthyaetus. However, the population is likely not considerably large despite its expansive range (Ferguson-Lees and Christie 2001). The species is considered rare and/or local in Nepal and Sri Lanka, uncommon and local in Bangladesh (Grimmett et al. 1998), and rare and scarce in Myanmar, Philippines, Cambodia and Singapore (Robson 2000, BirdLife International 2001); it may now be extirpated entirely from Lao PDR (Timmins et al. in press). The species is considered rare across most of South-East Asia (Ferguson-Lees and Christie 2001). The species is absent from the north and centre of Thailand, and disappearing from the north of Vietnam (from which there are almost no recent records: eBird 2024) and it is considered scarce in southern Thailand and Vietnam (Robson 2000). In Indonesia it is widely distributed but uncommon in Sumatra and Borneo (MacKinnon and Phillipps 1993). North-east India likely represents a stronghold for the species where it is considered widespread and frequent (Grimmett et al. 1998, Ferguson-Lees and Christie 2001).
There have however been few efforts to quantify population sizes. Several areas along the Mekong river in Cambodia were estimated to hold dozens of breeding pairs (Bezuijen et al. 2008), although the numbers appear to have drastically declined in Cambodia in recent years (Mittermeier et al. 2019). Miron and Chowdhury (2019) recorded 0.54 birds/km2 in Noakhali District, Bangladesh, and Tingay et al. (2006) recorded one breeding pair every 2.5 km2 in Tonle Sap Lake, Cambodia. These two studies demonstrate two regions that support sufficient food sources and consequentially localised and abundant breeding populations. However, given the species is likely to congregate in preferred breeding habitat, and there is little known about its abundance across much of its range, it is not possible to extrapolate these estimates to provide an estimation of the total population size. Therefore, the population size is unknown.
Trend justification
I. ichthyaetus is widespread but has suffered declines across most of its range. The species was formally widespread in the lowlands of Lao PDR, but has declined rapidly as a result of habitat loss and degradation (Fuchs et al. 2007, Timmins et al. in press) to the extent that the species may have become extinct in the country (Timmins et al. in press) or persists only in very small numbers (Thewlis et al. 1998, Fuchs et al. 2007, Bezuijen et al. 2008). Similar declines in Cambodia are also critical for the species, with at least two regionally significant breeding populations present along the Kratie to Lao PDR section of the Mekong (Bezuijen et al. 2008) and at Prek Toal, Tonya Sap Lake (Tingay et al. 2010). Three surveys carried out throughout 2007 along 130 km of riverine and floodplain habitat along the Mekong River recorded 150 sightings of an expected 40-60 breeding pairs (Bezuijen et al. 2008), but the species was only recorded once when the same region was revisited 10 years later (Mittermeier et al. 2019). The region was reportedly seriously impacted by human interference from selective logging for charcoal production and clearing for agriculture (Mittermeier et al. 2019, BirdLife International 2024). A logging company was also observed actively building roads and extracting timber (Mittermeier et al. 2019). Further impacts to the species likely include unsustainable fishing practices, such as poisoning which can lead to direct mortality, as well as explosives which can contribute to declining food sources (BirdLife International 2024). In comparison, surveys between 2005 and 2009 at Prek Toal recorded 60-80 occupied nests annually (Tingay et al. 2012), suggesting a reasonably stable breeding population. Although there have not been recent surveys of this population, the species is still frequently and consistently recorded at Prek Toal (eBird 2024) suggesting numbers are persisting. This population is threatened by the unsustainable harvesting of water snakes (a primary food source) by the local human population (Tingay et al. 2006, 2010) as well as the upstream construction of hydro-electric dams in Cambodia, as well as China, Laos, and Thailand which may disrupt the flood cycle at Prek Toal (Kummu and Sarkkula 2008) and increase mercury accumulation in food sources which can lead to reproductive failure (Jagoe et al. 2002). Severe declines are also suspected to be occurring in Indonesia, particularly in Sumatra where it was thought to be fairly numerous in the 1980s and 1990s (Holmes and Noor 1995, Clarke et al. 2023). The declines are at least partly attributable to the cage bird trade (Nijman et al. 2022, TRAFFIC 2024) but on Sumatra have probably been largely driven by the conversion of large areas of lowland forest to oil-palm and rubber plantations (Descal et al. 2021, Wang et al. 2023). The species is also declining in Thailand where it was formally widespread, Vietnam where it is rapidly disappearing from the north, Malaysia with only an estimated 40 pairs on the peninsula, as well as Philippines, and Cambodia (Robson 2000, Ferguson-Lees and Christie 2001, Fuchs et al. 2007, Clarke et al. 2023).
Conversely, populations in other regions appear to be stable, despite disturbance or highly modified areas in some cases. For example, the species is considered widespread and frequently encountered in north-east India (Clarke et al. 2023). Additionally, the species has stably bred in small numbers over several years in Chitwan, Nepal, despite overfishing, habitat loss and degradation, and pollution of waterways all cited as causes of waterbird declines in the region (BCN and DNPWC 2011, Adhikari et al. 2018). Provided there is a sufficient food source for the species, it appears that even human modified habitat can support large breeding densities. Miron and Chowdhury (2019) recorded 0.54 birds/km2 in Noakhali District, Bangladesh, an area with a high density of commercial fisheries, as well as human settlements and agricultural areas (Miron and Chowdhury 2019). The study found c. 77% of nests within 100 m of human settlements and c. 73% closer to commercial rather than non-commercial waterbodies. These numbers are comparable to breeding densities in Tonle Sap Lake, Cambodia (a natural swamp forest with little human disturbance; Tingay et al. [2010]) of one pair every 2.5km2 (Tingay et al. 2006), suggesting that the species can persist in disturbed areas as long as suitable nesting trees and food sources are present. Furthermore, the species may be increasing in abundance in Singapore (Clarke et al. 2023) due to this adaptability to urban waterbodies and the introduced prey items (Yong 2011).
There has been an estimated 28-33% loss of forest cover within the species range over the past-three generations (Global Forest Watch 2024, based on data from Hansen et al. [2013] and methods disclosed therein). However, forest loss alone is likely to overestimate population declines considering the species’ adaptability to modified areas (Yong 2011, Miron and Chowdhury 2019). Consequentially, continuing declines in the range of 20-29% are suspected.
I. ichthyaetus is widespread but generally scarce, occurring in peninsula and north-east India, Sri Lanka, Chitwan, Nepal, Bhutan, Bangladesh, down to Myanmar, southern Thailand, Cambodia, Vietnam, Sabah, Sarawak, and Peninsular Malaysia, Kalimantan, Sumatra, and Sulawesi Indonesia, Brunei, and the Philippines (BirdLife International 2001, Ferguson-Lees and Christie 2001, Clarke et al. 2023). The species may occur in Java, Indonesia (MacKinnon and Phillipps 1993), but it is incredibly rare, having only been recorded twice since the 1990s (eBird 2024) and is likely only an occasional visitor.
I. ichthyaetus occurs in lowland forest, closely associated with large bodies of freshwater, particularly sluggish streams and large ponds, primarily below 300m (Ferguson-Lees and Christie 2001, Clark et al. 2023). The species also occurs locally up to 1,500m (Ferguson-Lees and Christie 2001), and also frequents rivers, reservoirs, marshes, seasonally flooded swamp-forest, mangrove swamps, coastal lagoons, and estuaries (Ferguson-Lees and Christie 2001, Tingay et al. 2010, Yong 2011). The species also occurs in highly modified habitats such as irrigation tanks (Ferguson-Lees and Christie 2001), and a large breeding population is present in close proximity to commercial waterbodies in Bangladesh (Miron and Chowdury 2019).
The species' diet consists primarily of fish, including dead fish (Ferguson-Lees and Christie 2001, Clark et al. 2023). At least part of the species' diet also consists of reptiles (Tingay et al. 2006, Yong et al. 2011, 2014), particularly water snakes appear an important food source in Cambodia (Tingay et al. 2006). May also feed on terrestrial birds and small mammals (Ferguson-Lees and Christie 2001).
Most consistently, I. ichthyaetus is threatened by widespread deforestation and degradation of its habitat, in addition to more localised threats such as pollution, overfishing, and trade (Ferguson-Lees and Christie 2001, Clarke et al. 2023). Across the entire range, there has been an estimated 28-33% loss of forest cover within the species range over the past three generations (Global Forest Watch 2024, based on data from Hansen et al. [2013] and methods disclosed therein). However, the species has demonstrated adaptability to human modified areas, breeding near commercial waterbodies (Miron and Chowdhury 2019) and feeding on introduced species (Yong 2011). Regardless, there have still been localised declines of the species. For example, the species seems to have declined rapidly along the Mekong River in Cambodia where selective logging for charcoal production, clearing for agriculture, and unsustainable fishing practices, are extensive (Mittermeier et al. 2019, BirdLife International 2024). Similarly, the species may potentially be extinct in Laos (Timmins et al. in press), or at most very rare, as a result of similar pressures to Cambodia (Thewlis et al. 1998, Fuchs et al. 2007, Bezuijen et al. 2008). Therefore, the extent of cumulative localised threats are likely important as opposed to general widespread habitat loss. Additional more localised threats include over-harvesting of water snakes (a preferred local prey species) in Prek Toal, Cambodia (Tingay et al. 2006, 2010), the alteration of flood cycles from upstream construction of hydro-electric dams (Kummu and Sarkkula 2008), and overfishing and pollution of waterways in Nepal (BCN and DNPWC 2011, Adhikari et al. 2018). Additionally, in Indonesia, the species is threatened by both domestic and international trade (Nijman et al. 2022, TRAFFIC 2024), largely through online markets (Iqbal 2016, Gunawan et al. 2017, Nijman et al. 2022). The loss of forest cover generally is also the most acute in Indonesia (Global Forest Watch 2024), where losses are driven by the conversion of lowland forests into palm-oil and rubber plantations (Descal et al. 2021, Wang et al. 2023).
Conservation Actions Underway
None are known but it occurs in multiple protected areas.
61–75 cm; 1,500–1,600 g in males, and 2,300–2,700 g in females; wingspan 155–170 cm. Medium-sized brownish-gray fishing-eagle, with relatively small head and bill gray, and belly and base of tail white; iris yellow, with cere gray-brown to blackish-gray, and legs grayish-white to pale yellowish-gray. Female is usually larger than male by up to 23%, and apparently much heavier. Juvenile is brown, with underparts usually heavily streaked white (one specimen from Java was unstreaked); iris brown (not yellow). Similar species: Darker and duskier than Lesser Fish-Eagle (Icthyophaga humilis), which is more associated with foothills and faster-flowing waters, and has poorly marked subterminal tailband and small white flashes at base of primaries. Pallas's Fish-Eagle (Haliaeetus leucoryphus) is larger, with significantly longer but narrower wings, paler head, and dark abdomen, thighs and undertail coverts. Sounds: Often vocalizes at night, but only during breeding season; most frequently heard is a loud clanging which is far-carrying and resembles the voice of Indian Gray Hornbill (Ocyceros birostris); also a high-pitched scream, an owl-like ooo-wok, and loud gurgling calls.
Text account compilers
Richardson, L.
Contributors
Davidson, P., Naoroji, R., Benstead, P., Taylor, J., Westrip, J.R.S., Elliott, N., Ashpole, J & Mahood, S.
Recommended citation
BirdLife International (2024) Species factsheet: Grey-headed Fish-eagle Icthyophaga ichthyaetus. Downloaded from
https://datazone.birdlife.org/species/factsheet/grey-headed-fish-eagle-icthyophaga-ichthyaetus on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.