Aspects of the ecology of black grouse (Tetrao tetrix) in plantation forests in Scotland

Abstract

Aspects of the ecology of black grouse (Tetrao Tetrix), a species of international conservation concern, in commercial plantation forests were investigated between 1996 - 1998 at three study areas in Scotland. The aim was to identify the species' habitat and area requirements in first and second rotation forestry. The distribution of males was assessed using lek surveys and studied at two spatial scales in the mixed rotation forest landscape of Cowal, Argyll and at two spatial and temporal scales in highland Perthshire - a less afforested region. In addition, a radio-tracking study was undertaken to examine the habitat selection of broods in two first rotation plantations in north Perthshire. Pre-thicket forestry formed a preferred habitat but, in terms of lek distribution, black grouse did not differentiate between first and second rotation pre-thicket habitat patches. Patch size, the total amount of forestry in the area, the proportion that was pre-thicket stock and its level of fragmentation, however, were all correlated with the probability of a location holding a lek and the number of males attending it. Lek isolation reduced the number of males in attendance and increased the likelihood of the lek declining over time. Brood habitat preferences differed from those of adult birds. Broods selected habitats that were `open' enough to support a rich ground flora and presumably an adequate invertebrate fauna but also 'closed' enough to provide cover, representing a compromise between foraging potential and predation risk. Brood roost sites differed by having shorter trees but a higher degree of cover 1-1.5 metres above the ground. Results from the different study areas and age classes are compared and contrasted and the implications of the research findings for `black grouse friendly' forestry management are discussed. Finally, suggestions for further work are made.