Evaluation of a density index for territorial male Hazel Grouse Bonasa bonasia in spring and autumn

Abstrakti

A density index for territorial male Hazel Grouse Bonasa bonasia in spring and autumn is presented and evaluated. One whistles with a hunter's whistle every 30 seconds for 6minutes from census points located at 150-m intervals within the area to be censused, and responding Hazel Grouse are counted. Counts were conducted throughout days with little or no wind. The number of counted males was significantly and linearly correlated with the number of known territorial males on an intensive study area . There, 82% of the territorial males responded and were counted. Response rate appeared to be independent of density, based on counts in areas with a 20-fold variation in densities. When censuses were repeated, both results were similar. Within the conditions of these counts, no effects of weather or date were found. However, Hazel Grouse responded less at midday. Using this method, one can count Hazel Grouse at a rate of about 5 minutes per ha along transects and 5-9 minutes per ha on blocks of habitat, depending on plot size . I recommend that censuses be conducted during 4-5 weeks prior to laying in spring and during 4-5 weeks after brood dissolution in autumn .