Koshi Tappu Wildlife Reserve is a paradise for bird watchers, with an area of 175 square kilometers. The park is situated on the bank of the Sapta Koshi River. The vegetation consists mainly of grassland, scrub and deciduous forests. The reserve is unique for its 100 or so surviving wild water buffaloes. Other mammals found are the hog deer, wild boar, and the Nilgai. There are a total 280 species of birds here including 20 ducks, two ibises, many storks, egrets and herons, the endangered swamp partridges and Bengal floricans. The region is a resting-place for migrating birds not seen anywhere else in Nepal. The endangered Gharial crocodile and Gangetic dolphin have also been sighted in the Koshi River.