Sibsagar Tanks

Country/territory: India

IBA criteria met: A1, A4i (2004)
For more information about IBA criteria, please click here

Area: 150 ha

Bombay Natural History Society
IBA conservation status
Year of assessment (most recent) State (condition) Pressure (threat) Response (action)
2003 not assessed low not assessed
For more information about IBA monitoring, please click here

Site description (2004 baseline)
This IBA site includes three large historic tanks Joysagar (60 ha), Sivasagar (50 ha) and Gourisagar (40 ha) and their high banks in and around Sibsagar town in eastern Assam. Since time immemorial, birds have been protected in these sacred temple tanks. Every winter hundreds, often thousands, of ducks and geese spend the whole day resting and feeding on these tanks, which are easily accessible by metalled roads. The surrounding terrain is flat plain country. Sibsagar and Joysagar tanks are known for their spectacular flocks of ducks and geese. The largest wintering flocks of Bar-headed Anser indicus and Greylag Anser anser geese ever recorded in Assam, were in Joysagar tank. About 5,800 and 3,000 respectively were counted in 1995 (Bibhab Talukdar in Choudhury 2000). Most of the tanks are open water but on the margins there is emergent and floating vegetation. Fortunately, these tanks are free from Water Hyacinth Eichhornia crassipes.

Key biodiversity

AVIFAUNA: More than 60 species of birds have been recorded on the waterspread as well as in the trees on the banks. Lesser Adjutant Leptoptilos javanicus and Greater Adjutant L. dubius are seen in the trees growing around the tanks. Choudhury (1988) has seen seven Baer’s Pochard Aythya baeri on Sibsagar tank in 1988, amongst thousands of other ducks. Great Crested Grebe Podiceps cristatus, is seen in Sibsagar and Joysagar tanks, sometimes in hundreds. Before return migration, they appear in breeding plumage and territorial display is seen. Both the Bar-headed and Grey geese are present in large numbers, much above their 1% biogeographic population threshold, as recently determined by Wetlands International (2002). For example, between 52,000 to 60,000 Bar-headed Goose are estimated in the world, with 1% population threshold of 560. It is not uncommon to see 1-2 thousands in these tanks. In 1995, a total of 5,800 were counted, which constitute about 10% of the population. Similarly, the South Asian non-breeding population of the Greylag Goose Anser anser rubirostris is estimated to be 15,000 (Wetlands International 2002). With a total of 3,000 found in these tanks in 1995, it constitutes nearly 20% of this biogeographic population. Thus, this site easily qualifies A4i criteria.

OTHER KEY FAUNA: As these tanks are surrounded by human habitation, no large wild mammal is present. Only Smooth Indian Otter Lutrogale perspicillata occasionally fish in the tanks, but they are now extremely rare. Among reptiles, large softshell turtles have been recorded.

Key contributors: Diptimanta Barooh, Anwaruddin Choudhury and Kulojyoti Lahkar.

Recommended citation
BirdLife International (2023) Important Bird Area factsheet: Sibsagar Tanks. Downloaded from on 07/12/2023.