The Biebrza valley supports a unique group of bird species in Europe. About 270 species have been observed here so far, including 181 breeding birds. Among 56 species recorded in Polish Red Data Book of Animals (1992), 17 breed in the Park, e.g.: Spotted Eagle Aquila clanga, Great Snipe Gallinago media, Black Tern Chlidonias niger, Aquatic warbler Acrocephalus paludicola. For some waterfowl species, Biebrza marshes are among the last refuges for the survival of their population in Central Europe. For many groups of animals, there are only sporadic data. So far 48 mammal species, 13 amphibian species, 5 species of reptiles, 36 species of fish and Ukrainian lamprey, over 750 species of moths and butterflies, 500 species of battles, 11 species of bats, 42 species of caddis-fly, about 450 species of spiders and 19 of leeches have been recorded.