The Karikili Bird Sanctuary is constituted by two rain-fed non-perennial irrigation tanks spreading over an area of 58.442 ha. It was declared a sanctuary in 1972. It exhibits a flat topography with undulating and gentle slopes in parts and is situated 100 m above MSL. North east and South west monsoons contribute 54% and 36% of the total annual rainfall. SW monsoon is highly erratic and summer rains are negligible. Rainfall fluctuates greatly from year to year varying from 400 mm to almost 1700 mm, flooding the area in the months of monsoon (July - September). The vegetation in Karikili tanks is mainly composed of Barringtonia acutangula and Acacia niloticatrees, raised as plantations by the Forest Dept. Surrounding vegetation is composed of scrub and thorn. There are also grass species like Typha, “Korai”, Naanal grass and Cynodon dactylon, etc on higher islets. The habitat abutting the sanctuary is a complex of grass-scrub-palmyra. This Borassus flabellifer (Panai in Tamil) forms a significant part of the landscape supporting dependent biodiversity including avifauna, playing an important role in the livelihood of the people. The main fauna includes a variety of resident and migratory avifauna. This includes mainly waterfowl, water birds, and a few species of scavengers. Near threatened Oriental Darter and Spot-billed Pelican breeds here. The Karikili Bird Sanctuary has a history of people’s cooperation in protecting water birds which in turn provides guano effect of the supply of nutrient-enriched water to Karikili crop fields.

A wetland should be considered internationally important if it contains a representative, rare, or unique example of a natural or near-natural wetland type found within the appropriate biogeographic region.

A wetland should be considered internationally important if it supports vulnerable, endangered, or critically endangered species or threatened ecological communities.

A wetland should be considered internationally important if it supports populations of plant and/or animal species important for maintaining the biological diversity of a particular biogeographic region.

A wetland should be considered internationally important if it supports plant and/or animal species at a critical stage in their life cycles, or provides refuge during adverse conditions.

A wetland should be considered internationally important if it regularly supports 20,000 or more waterbirds.

A wetland should be considered internationally important if it regularly supports 1% of the individuals in a population of one species or subspecies of waterbird.

A wetland should be considered internationally important if it supports a significant proportion of indigenous fish subspecies, species or families, life-history stages, species interactions and/or populations that are representative of wetland benefits and/or values and thereby contributes to global biological diversity.

A wetland should be considered internationally important if it is an important source of food for fishes, spawning ground, nursery and/or migration path on which fish stocks, either within the wetland or elsewhere, depend.

A wetland should be considered internationally important if it regularly supports 1% of the individuals in a population of one species or subspecies of wetland-dependent nonavian animal species.