Ousteri Lake (18344)
India, Asia
Site overview
KBA status: confirmed
Year of last assessment: 2004
National site name: Ousteri Lake
Central coordinates: Latitude: 11.9475, Longitude: 79.7370
System: marine, terrestrial
Elevation (m): 10 00
Area of KBA (km2): 8.46887
KBA classification: Regional
Legacy site: Yes
Site details
Site description: Ousteri lake is located partly in Pondicherry and partly in Tamil Nadu near Ossudu village in the Villanur commune panchayat, about 12 km from Pondicherry, north of the Kaveri river. The lake depends on its catchment for 75% of its water, the rest comes from diversion channels. The lake is fed by local run-off and an intermittent river and has a bund on its western bank. It has an average depth of 1 m and dries up completely in summer. Besides being an internationally important site for migratory birds, the lake’s most valuable use is for irrigation. The lake has rich floral diversity of over 200 species of plants belonging to 60 families. Part of the bund is well protected by trees. It has extensive aquatic flora of the floating, submerged and emergent type.
Rationale for qualifying as KBA: This site qualifies as a Key Biodiversity Area of international significance that was identified using previously established criteria and thresholds for the identification of Important Bird and Biodiversity Areas (IBAs) and for which available data indicate that it does not meet global KBA criteria and thresholds set out in the Global Standard.
Additional biodiversity: AVIFAUNA: Ousteri is an important area for migratory waterfowl and regularly holds over 20,000 birds belonging to more than 40 species (Balachandran and Alagarrajan, 1995; Jhunjhunwala 1998). Balachandran and Alagarrajan (1995) have also conducted monthly surveys for a year. According to their census figures, many species occur much above their 1% threshold level, determined by Wetlands International (2002). For example, they have reported 10,500 Little Cormorant Phalacrocorax niger in June and 12,000 in August. According to Wetlands International (2002), the total number of Little Cormorant in South Asia is 150,000, which means that about 7% are found in Ousteri. Similarly, the number of Eurasian Wigeon Anas penelope can go up to 4,600 in February, while the 1% threshold is 2,500 (Wetlands International 2002). It means that nearly 2% of the biogeographic population congregate at Ousteri before migration. Information on the global population of the Cotton Pygmy Goose or Cotton Teal Nettapus coromandelianus is lacking (Wetlands International 2002) so we do not know the 1% population threshold. At Ousteri, Balachandran and Alagarrajan (1995) have noted up to 2,400 in June. This is one of the largest known congregations of this species in south India. The Cotton Pygmy Geese congregate here, as most of the wetlands dry up in summer, and large wetlands such as Ousteri have some water left. In India, Common Coot Fulica atra is resident in south India, while purely migratory in north India (Ali and Ripley 1987; Grimmett et al. 1998). In winter, the resident population is augmented by migratory birds from the temperate regions. This IBA is extremely important for the resident Coot population because when smaller wetlands are dry, Ousteri provides them refuge. In their one year monitoring of birds at Ousteri, Balachandran and Alagarrajan (1995) found that the maximum number of Coots, about 11,000, was found in the peak summer month of June. In July, the number came down to 9,000 as some birds probably moved to interior wetlands where rains had started, but the real change took place in August and September when 2,800 and 650 coots respectively were left. In winter months from October to February, the maximum number of Coots seen at Ousteri was 450. This further proves the importance of maintaining a chain of wetlands (IBAs), not only for rare species but also for such common species like the Coot. The Red Data Book species seen at Ousteri in 1994-95 are: Spotbilled Pelican Pelecanus philippensis (maximum of 6 seen in April 1994), Darter Anhinga melanogaster (maximum 2), Painted Stork Mycteria leucocephala (115 counted in September 1994), Eurasian Spoonbill Platalea leucorodia (only 6 seen in June 1994) and Black-headed Ibis or White Ibis Threskiornis melanocephala (up to 200 counted in June 1994) (Balachandran and Alagarrajan 1995. OTHER KEY FAUNA: As this is basically a wetland surrounded by agricultural fields and human habitation, no mammal or reptile of conservation concern is found here.
Habitats
Land use: fisheries/aquaculture | urban/industrial/transport | water management
| IUCN Habitat | Coverage % | Habitat detail |
|---|---|---|
| Wetlands(Inland) | 100 |
Threats
Summary of threats to biodiversity at KBA: MAIN THREATS: Fisheries; Filling in of wetlands; Poaching; Tourism. The Ousteri lake is used for fishing, supplies water for irrigation and plays a crucial role in recharging the aquifers. The lake is heavily silted and has reduced to 80% of its original area. Excessive grazing by livestock occurs. Waterfowl are poached by netting and shooting. Fishing, grazing of livestock and harvesting of reeds and aquatic vegetation are done by villagers living in the periphery of the lake. In order to allow free movement of fish nets, fishermen remove Vallisneria spiralis, one of the food plants of birds. The gill nets too, when left alone for long periods in water, entangle Grebe and other birds (Balachandran and Alagarrajan 1995). Another problem of Ousteri and other wetlands of Pondicherry is the spread of aquatic weeds such as Ipomoea cornea and Eichhornia crassipes. There are plans to develop the lake as a holiday resort with hotels and sporting facilities to cater to the inhabitants and tourists of Pondicherry. Water sports would cause excessive damage to the nesting birds. As Ousteri is one of the most important wetlands of south India, it should be declared a Sanctuary and strict protection should be provided to birds. The Forest Department should develop a management plan, in collaboration with local villagers, fishermen, naturalists and officials of the Irrigation Department, to derive maximum benefit both for the local people and birds.
| Threat level 1 | Threat level 2 | Threat level 3 | Timing |
|---|---|---|---|
| Agriculture & aquaculture | Livestock farming & ranching | Small-holder grazing, ranching or farming | Ongoing |
| Invasive & other problematic species, genes & diseases | Invasive non-native/alien species/diseases | Named species | Ongoing |
| Biological resource use | Hunting & collecting terrestrial animals | Intentional use (species being assessed is the target) | Ongoing |
| Biological resource use | Fishing & harvesting aquatic resources | Unintentional effects: subsistence/small scale (species being assessed is not the target) [harvest] | Ongoing |
| Biological resource use | Gathering terrestrial plants | Unintentional effects (species being assessed is not the target) | Ongoing |
| Pollution | Agricultural & forestry effluents | Soil erosion, sedimentation | Ongoing |
| Human intrusions & disturbance | Recreational activities | Only in the future | |
| Residential & commercial development | Tourism & recreation areas | Only in the future |
Additional information
References: Ali, S. and Ripley, S. D. (1987) Compact Handbook of the Birds of India and Pakistan (Second Edition). Oxford University Press, Delhi. Balachandran, S. and Alagahrajan, R. (1995) An ecological survey of the wetlands of Pondicherry with special reference to Ousteri lake. Institute of Restoration of Natural Environment, Nagercoil. Pp. 40. Grimmett, R., Inskipp, C. and Inskipp, T. (1998) Birds of the Indian Subcontinent. Christopher Helm Ltd., London, U.K. Jhunjhunwala, S. (1998) The ornithological importance of Ousteri lake and Bahour lake: A study of the habitat preferences of their waterfowl and waders. M.Sc. Dissertation. Salim Ali School of Ecology and Environmental Sciences, Pondicherry University. Wetlands International (2002) Waterbirds Population Estimates: Third Edition. Wetlands International Global Series No. 12. Wageningen, the Netherlands.