RESPONSES OF GREY WAGTAIL MOTACILLA-CINEREA TO CHANGING PREY AVAILABILITY DURING THE NESTING PERIOD

Few studies are available on the responses of birds to fluctuations in prey abundance during the breeding season. The aim of this study was to study such responses of Grey Wagtails Motacilla cinerea. Prey avail ability varied significantly, and often very rapidly, on both a tempor al and a spatial scale. Grey Wagtails were able to keep track of chang es in prey availability and to switch between foraging sites. The use of foraging sites changed during the breeding period and in different weather conditions. During periods with high prey availability, 95% of prey capture attempts were recorded in the stream bed and specific ki nds of prey, or prey of large body size, were selected. However, durin g periods of food scarcity, Grey Wagtails switched to hunt mainly for drifted invertebrates on roads etc. The results show that Grey Wagtail s were able to optimize foraging behaviour in a changing environment.