Chilika Lake is a brackish water lagoon on the east coast of Odisha with an area of 1,105 km2. It is connected to the Bay of Bengal by a 35-km-long narrow channel and is a part of the Mahanadi delta. In the dry season, the tides bring in salt water. In the rainy season, the rivers falling into the lagoon decrease its salinity. Birds from places like the Caspian Sea, Lake Baikal, other parts of Russia, Central Asia, South-East Asia, Ladakh and the Himalayas migrate to the lagoon in winter. Among the birds spotted there are Eurasian wigeon, pintail, bar-headed goose, greylag goose, flamingo, mallard and Goliath heron. The lagoon also has a small population of the endangered Irrawaddy dolphins. The state's coastal region has also had sightings of finless porpoise, bottlenose dolphin, humpback dolphin and spinner dolphin in its waters.