Abundance of male Black Grouse Tetrao tetrix in Britain in 2005, and change since 1995–96

Abstract

Capsule There was a non-significant decline in the number of displaying males in Britain between 1995–96 and 2005, with a significant decline in Scotland. Aims To estimate the number of displaying male Black Grouse in Britain in 2005, and to compare this with the 1995–96 estimate. Methods Surveys were carried out in a stratified sample of 1-km (Wales) and 5-km (Scotland and England) squares throughout the known range, using similar methods to the 1995–96 survey. Results There were an estimated 5078 displaying males in Britain in 2005 (95% CI 3920–6156). This estimate is 22% less than the 1995–96 estimate of 6506, although these estimates are not significantly different. In Scotland, numbers fell by 29% overall, comprising large and significant declines of 49% and 69% in southwest and southeast Scotland, respectively, but small and non-significant declines in north (16%) and northeast Scotland (9%). In England, there was a non-significant decline of 11%, while in Wales numbers rose by 39%. Where numbers have declined there has been a decrease in the number, but not the size, of display groups. Display sites in Britain were at higher altitudes (median 400 m) in 2005 than in 1995–96 (median 340 m). Conclusion Although Black Grouse numbers in Wales increased, this survey provides evidence of a large decline in southern Scotland. The causes of this decline are not fully understood, and further research is urgently required to reveal the underlying mechanisms and implement appropriate conservation measures.