CHANGES IN ABUNDANCE AND SELECTION OF FORAGING HABITAT IN CORMORANTS PHALACROCORAX-CARBO IN SOUTH BOHEMIA (CZECH-REPUBLIC)

The breeding population of the Cormorant Phalacrocorax carbo sinensis in south Bohemia increased since its establishment in 1983. However, numbers of breeding pairs began to decrease after 1988. The relationship between Cormorant numbers during the breeding season and habitat and fish stock characteristics was investigated on 197 ponds in Trebon Landscape Protected Area. Out of 749 Cormorants recorded, 92.3% were observed on (1) ponds located in distance less than 10 km from the breeding colony, and (2) ponds with water surface area larger than 20 ha. The Cormorants preferred ponds with water depth of 1-2 m, surrounded by wood and well developed shore line. 87% of Cormorants occurred on ponds with Carp Cyprinus carpio older than 1 year. Among ponds without breeding colony, the Cormorants prefer fish sized between 100-200 mm.