Status of male Black Grouse Tetrao tetrix in Britain 1995-96.

Abstract

A survey of the male Black Grouse Tetrao tetrix population in Britain was undertaken in 1995 and 1996. The survey was based on counts of males displaying in the spring. In Wales and Staffordshire, the entire known population was surveyed. In northern England and Scotland, a stratified random sample of 5-km squares, representing approximately 8% of the species' range, was surveyed. In survey squares, surveyors searched all apparently suitable habitat between late March and early May, and counted any displaying males at dawn. Densities on survey squares varied from zero to 2.4 displaying males per km² of apparently suitable habitat. The British population of spring-displaying male Black Grouse was estimated as 6510 (95% confidence limits 5000-8100). Regional population estimates are presented. Analysis of the survey results and a special validation study highlighted a number of potential sources of error. Ways of improving any future surveys, while retaining repeatability, are suggested. The national population estimate produced by this survey is well below other recent published estimates and provides further evidence of a serious decline for the British Black Grouse.