Vast areas of tropical swamp and deltas are found in the Indomalayan ecozone, where great rivers, fed by the snow and glaciers of the mighty Himalayas, wander across the lowlands and empty into the Indian Ocean. Mangrove swamps develop at the ocean's edge on the mud banks built up by debris deposited by the rivers. The mangrove swamp usually blends into the tropical forest on the drier land, and many of the tree creatures that live here are the same as those further inland.The swamps are home to a great many ray-finned fish and other aquatic animals, particularly those that can withstand the conditions of both saltwater and freshwater. They also support vast numbers of wading birds and pterosaurs that feed on the fish and the mud creatures. The paraso is one of the oddest of such animals. It is a pterosaur that hunts in the shallow lagoons and backwaters of the swamps. It is quite large, with a wingspan of about 3 meters (10 feet). The wings are brightly colored and make a dazzling display as the pterosaur launches itself into the air and flies off over the swamp. The wings, however, have another function. They are used as a kind of a trap in order to lure and catch fish in a way that is totally unlike any other in the animal kingdom.