Udayamarthandapuram is one of the important Birds Sanctuaries in Tamil Nadu, one km off East Coast Road connecting Chennai and Kanyakumari. It is under the administrative jurisdiction of Thiruthuraipoondi taluk, Muthupet Block, located on Mannargudi – Udayamarthandapuram road. It is well known for sighting a large number of globally EN Asian Openbill Stork. Created in 1998 in Tiruvarur District it is near the confluence of Baminiyar-Kannanaar rivers, covering 43.767 ha. The sanctuary is a seasonal wetland fed by small canals receiving water from Mettur Dam through the Koraiyar canal. The southern part of the landscape is partly Koraiyar River running W to E and draining into Muthupet mangroves. It remains dry from April to August, during which small (artificial) tanks in the sanctuary store water to sustain the resident bird population. The wetland is representative of flat topography encompassing floodplains along rivers/streams, within the Cauvery delta& agricultural ecosystems. The vegetation cover serves as a good habitat for several birds, butterflies &other fauna. The site is an important staging and breeding ground for several species of waterbirds. The notable species observed at the site are oriental darter, glossy ibis, grey Heron &Eurasian spoonbill. It is one of the important breeding sites for the darter & Eurasian spoonbill. Udhayamarthandapuram stores floodwaters during monsoon overflows and maintains surface water flow during drier periods.

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.