Ganges Delta trees are found in these areas. The delta region has mangrove trees. It is estimated that 30,000 chital ("Axis axis") are in the Sundarbans part of the delta. Birds found in the delta include kingfishers, eagles, woodpeckers, the shalik ("Acridotheres tristis"), the swamp francolin ("Francolinus gularis"), and the doel ("Copsychus saularis"). Two species of dolphin can be found in the delta: the Irrawaddy dolphin ("Orcaella brevirostris") and the Ganges river dolphin ("Platanista gangetica gangetica"). The Irrawaddy dolphin is an oceanic dolphin which enters the delta from the Bay of Bengal. The Ganges river dolphin is a true river dolphin, but
Endangered Species Act of 1973 habitat protection and recovery goals, requiring the identification and protection of all lands, water and air necessary to recover endangered species. To determine what exactly is critical habitat, the needs of open space for individual and population growth, food, water, light or other nutritional requirements, breeding sites, seed germination and dispersal needs, and lack of disturbances are considered. As habitat loss is the primary threat to most imperiled species, the Endangered Species Act of 1973 allowed the Fish and Wildlife Service (FWS) and National Marine Fisheries Service (NMFS) to designate specific areas as protected "critical habitat" zones. In 1978, Congress