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

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. To produce an updated estimate of the number of Western Capercaillies in Scotland. Line transects were surveyed across the current distribution, samp...

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Veröffentlicht in:Bird study Jg. 71; H. 1; S. 17 - 31
Hauptverfasser: Wilkinson, Nicholas I., Doubleday, Molly, Douse, Andrew, Ford, Andy, Kelly, Leah A., Kortland, Kenny, Titherington, Juli, Wotton, Simon R., Ewing, Steven R.
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Thetford Taylor & Francis 02.01.2024
British Trust for Ornithology
Schlagworte:
adults
Biological surveys
birds
Breeding
Breeding success
confidence interval
Confidence intervals
Current distribution
extinction
Males
Population characteristics
Population statistics
Sampling
Scotland
Sex
Sex ratio
Species extinction
Surveys
Survival
Tetrao urogallus
Winter
United Kingdom > UK
Scotland
ISSN:0006-3657, 1944-6705, 1944-6705
Online-Zugang:Volltext
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Zusammenfassung: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. To produce an updated estimate of the number of Western Capercaillies in Scotland. 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. 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. 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.
Bibliographie:ObjectType-Article-1
SourceType-Scholarly Journals-1
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ISSN:0006-3657
1944-6705
1944-6705
DOI:10.1080/00063657.2023.2286298