In a remarkable display of reverse migration, an endangered Pallas’s fish eagle tagged in Mongolia has returned to Kaziranga National Park in Assam for the fifth consecutive winter breeding season.
The eagle, named Ider, was tagged with ring A25 at Buuntsagaan Lake in Central Western Mongolia on 21 August 2020, according to Dr Batmunkh of the Wildlife Science and Conservation Centre (WSCC). The bird has since been observed returning annually to Kaziranga, altering its nesting location only once during these years. Scientists from the Bombay Natural History Society (BNHS) recorded the eagle in Kaziranga this year on 16 March.
Dr Batmunkh stated that Ider visits Mongolia’s Buuntsagaan Lake during the non-breeding season, from June to September.
The Pallas’s fish eagle (Haliaeetus leucoryphus), among the largest of fishing eagles, is listed as “endangered” on the International Union for Conservation of Nature (IUCN) Red List. Once considered locally common across central and southern Asia, the species has seen sharp declines in recent decades. Once widespread in regions such as the Caspian and Kazakhstan, the bird is now believed to have vanished from these former strongholds.
Its conservation status was first downgraded to “vulnerable” in 2016, and then to “endangered” in 2021. BirdLife International estimates the population of mature individuals to range between 2,500 and 9,999 globally.
Highlighting the ecological importance of Kaziranga, Dr Sonali Ghosh, Field Director of Kaziranga National Park and Tiger Reserve, said: “Kaziranga is one of the best locations to watch the Pallas’s Fish eagle in the world. The bird exhibits interesting ‘reverse migration’ behaviour as it breeds in Kaziranga during winter and migrates to Mongolia thereafter.”
Kaziranga National Park lies at the heart of the Central Asian Flyway (CAF), one of nine global migratory waterbird flyways, which includes routes from Siberia to the Maldives and the British Indian Ocean Territory. The CAF spans 30 countries across North, Central and South Asia, encompassing 279 populations of 182 migratory waterbird species.
India hosts around 370 migratory bird species, of which 310 rely on wetland habitats. The country’s vast network of wetlands—covering more than 15 million hectares—offers essential support to waterbird species. North-eastern India, particularly Kaziranga, serves as a critical wintering ground for both the CAF and the East Asian-Australasian Flyway (EAAF).
Despite the global importance of bird migration, Dr Ghosh noted that fewer than one per cent of bird species in India have been studied through satellite telemetry, leaving many migratory patterns undocumented.
“Kaziranga has a conservation legacy of over 119 years. With its terrestrial and aquatic habitats, it is one of the finest protected areas in the world. The Tiger Reserve is a popular destination for birders, owing to a very high diversity of over 500 bird species,” she added.
The Kaziranga Tiger Reserve extends over 1,302 square kilometres, with more than half its landmass consisting of grasslands and water bodies—locally referred to as beels. These, along with the Brahmaputra River and its tributaries such as the Dhansiri, Difloo and Laokhowa Suti, create ideal habitats for resident and migratory birds alike.
Kaziranga National Park (IBA Code: IN-AS-03) and Laokhowa and Burhachapori Wildlife Sanctuaries (IBA Code: IN-AS-02) are recognised as Important Bird Areas (IBAs). The sixth Kaziranga Waterbird Count, held on 11–12 January 2025, recorded 124 species of water and wetland-dependent birds, with a total of 112,062 individual birds from 25 families observed across 189 beels.
Sixty-two of the 124 species were winter migrants. Notable sightings included the Critically Endangered Baer’s Pochard and the Endangered Pallas’s Fish Eagle. The highest count was that of bar-headed geese, which numbered 20,845 individuals. For the first time, five new species were recorded in the region—knob-billed duck, Baer’s pochard, falcated duck, white-tailed eagle, and greater white-fronted goose.
Taking to X, Assam Chief Minister's Office shared the news of the arrival of the endangered bird from Mongolia, stating, “The endangered Pallas's Fish Eagle, tagged in Mongolia, has made Kaziranga its breeding ground for five straight years, putting Assam on the map of epic bird migrations. Witnessed these winged wonders.”
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