Spatial behaviour of first-year Blackcaps (Sylvia atricapilla) during the pre-migratory period and during autumn migratory stopovers

The spatial distribution of Blackcaps (Sylvia atricapilla) was Studied on the basis of ringing recaptures during the post-fledging period and during autumn migratory stopovers on the Courish Spit of the Baltic Sea. The distribution of distances between capture locations of individual birds was compared with the simulation model assuming random movements. During the pre-migratory period, the movements of Blackcaps did not significantly differ from the random pattern. During migratory stopovers, the birds remained within home ranges which were clearly smaller than the study site but still too large to be defended territories. This is suggested to be caused by different diets during pre-migratory and migratory periods and by different spatial distribution of the preferred food.