Density changes and habitat shift of great grey shrike Lanius excubitor during the non-breeding season

Abstract

Bird population density and their behaviour during non-breeding periods are determined mainly by meteorological conditions which force birds to use alternative strategies — migration to areas with more advantageous conditions or adaptation to existing conditions. During the 2002/03–2004/5 non-breeding seasons in the open habitats of the Kotlina Orawsko-Nowotarska valley (S Poland) studies on population dynamics, behaviour and habitat use of great grey shrike were conducted. Results were grouped into four meteorological periods (autumn, early winter, winter and early spring). Density changes were seen between subsequent seasons (from 0.34 to 1.9 ind./10 km), as well as between meteorological periods (from 0.48 to 2.70 ind./10 km). Perching was the most frequently observed behaviour. The foraging habitats used changed in frequency. In subsequent meteorological periods a decrease of open habitats used was noted with a simultaneous increase in afforestations used. These changes did not depend on lasting snow cover. Changes in vegetation type used during hunting were not observed. Great grey shrikes most frequently used natural perches (trees, shrubs and high vegetation).