Foraging and diving patterns of the Great Crested Grebe Podiceps cristatus in a fishpond

Abstract

Diving and foraging patterns of the Great Crested Grebe Podiceps cristatus were studied on Vrbje fishpond in Central Slovenia. Three pairs and their 10 young were studied. The duration of 348 dives of the six adults before hatching, 295 dives of the three pairs of adults with young, and 185 dives of the immature birds were recorded during the breeding season in 1998 (from June through October). Mean dive duration was 31 sec for adults before hatching, 41 sec for adults with young, and 25 sec for immatures. Diving success varied significantly between groups, the most successful were grebes with young. Adult grebes without young caught a higher proportion of large fish than the other groups did. Fish size was negatively correlated with duration of dives in adult grebes without young and in adults with young but not in immatures.