Further declines of the Western Capercaillie Tetrao urogallus in Scotland as shown by the 2021-2022 winter survey

Capsule: The estimated number of Western Capercaillies Tetrao urogallus in Scotland in winter 2021-2022 was 532 with a 95% confidence interval (CI) of 227-810.Aim: To produce an updated estimate of the number of Western Capercaillies in Scotland.Methods: Line transects were surveyed across the current distribution, sampling in two separate strata: a primary stratum in the core range and a secondary stratum in peripheral areas. Multi-covariate distance sampling was used to fit alternative detection functions to the sighting data, deriving national, regional and sex-specific estimates of abundance.Results: The survey recorded 115 Western Capercaillies in 104 separate encounters across 635 transects, yielding a population estimate of 532 individuals (95% CI: 227-810). This estimate was 52% lower than from the population survey in 2015-2016 (1114 individuals, 95% CI: 805-1505). Declines were greater for females than for males, leading to an adult sex ratio in favour of males. Most of the population (80%) continues to be concentrated in the region of Badenoch and Strathspey.Conclusion: With the population at its lowest level since the start of national monitoring in 1992-1994, the likelihood of extinction in Scotland for a second time seems inevitable without a step-change in conservation action. Measures to improve breeding success and survival are needed and should be targeted in the core of the range to maximize impact on the population.