Colonial waterbirds and their habitat use in the Danube Delta : as an example of a large-scale natural wetland

During the breeding seasons of 2001 and 2002 two comprehensive surveys of colonially breeding waterbirds (Pelecaniformes, Ciconiiformes and Charadriiformes) were carried out in both the Romanian and Ukrainian parts of the Danube Delta. Apart from being the first time in history that this internationally important area for these groups of birds was comprehensively surveyed, the aim of this study was also to obtain some insight in which are the crucial factors responsible for site selection and population size of colonial waterbirds.