Abstract
The role of waterbirds as indicators of trophic status of water-bodies was first outlined by the Finish ecologist Pontius Palmgren (PALMGREN 1936) , who distinguished three types of Finish lakes: i.e. Gavia-See (oligotrophic lakes), Podiceps-See (mesotrophic lakes) a Nyroca-See (ethrophic lakes).
Some decades later, waterbird data started to be used widely for the identification of wetlands of international importance.