Dispersal and migration of female Black Grouse Tetrao tetrix in eastern central Finland

摘要

We studied the movement patterns of 209 female Black Grouse radio-marked during 1990-1993 in eastern central Finland. Females were captured for marking in late winter, and the transmitters had a life expectancy of 6-10 months. Adults tended to initiate spring movement to breeding range earlier than yearlings. The median net distance between the marking (winter) site and nest site was 2.6 km for adults and 9.2 km for yearlings, and the maximum distances recorded were 29.6 and 33.2 km, respectively. The spring dispersal directions of yearlings differed from a uniform distribution. Data from radio-tracking, recapturing and recoveries from the public revealed that females that moved less than the median distance in spring as yearlings tended to show fidelity to their first winter range. In contrast, those individuals that moved more than the median distance, mostly switched to using a new winter range. Females marked as adults tended to show fidelity to their winter range. The longest migratory movement recorded between breeding and winter range was 19 km. We conclude that female Black Grouse possess good dispersal abilities, and had no movement problems in our study area consisting of a managed forest landscape.