A small indian boy plays with his arrow and bow at the margins of Araguaia river, one of the major rivers of Brazil, and the principal tributary of the Tocantins, Amazon rainforest. Roughly in the middle of its course, the Araguaia splits into two forks (with the western one retaining the name Araguaia and the eastern one being called Rio Javaés). These later reunite, forming the Ilha do Bananal, the world's largest river island. The mouth of the Javaés forms a broad inland delta where it pours back into the main Araguaia, a 100,000 hectare expanse of igapó flooded forest, blackwater river channels, and oxbow lakes called Cantão. This is one of the biologically richest areas of the eastern Amazon, with over 700 species of birds, nearly 300 species of fish (more than in all of Europe), and large populations of threatened species such as the giant otter, the black cayman, and the world's largest freshwater fish, the pirarucú, all occurring within a relatively small area. "Araguaia" means "River of the Macaws" in the native Tupi language.