Estimating capercaillie Tetrao urogallus population size in Scotland from annual leks and counts of broods over the period 2010–2020

Abstract

The population size of capercaille Tetrao urogallus in Scotland was estimated from annual counts of males at 151 known spring lek sites and 45 counts of males, females and their broods in August during the period 2010–2020, combined with published survival estimates. Population size declined from an estimated 580 birds (95% CL: 462–698) in 2011 to 304 (239–369) in 2020 and the extinction probability was 23% after 25 years, 95% after 50 years and 100% after 100 years. Removing mortality associated with collisions against fences lowered extinction probabilities to 0, 3 and 40% respectively, emphasizing fence removal as a management priority. Greatest declines occurred in Deeside and Donside, Morayshire and Ross‐shire and Perthshire and Trossachs. In the Badenoch and Strathspey stronghold, where an estimated 83% of males remain, numbers of occupied leks and lekking males have decreased in the last five years and are associated with reduced breeding success over the last 10 years. Our estimates of population size are only half that derived from the last official national survey in winter 2015/2016. We discuss possible reasons for this difference including underestimates from lek‐based surveys linked to male detection probabilities. Finally, we recommend improvements to the current annual monitoring scheme, including repeat counts at leks and use of novel remote acoustic devices and restoration of annual brood counts in remaining key forests.

Evaluating diversionary feeding as a method to resolve conservation conflicts in a recovering ecosystem

“…Management includes intense culling of Cervidae (red and roe deer) to allow forest regeneration, and, unlike in more traditional neighbouring estates, there is no control of predators. The area encompasses the core of the remaining population of Scottish capercaillie (Baines & Aebischer, 2023). The predator community includes badger, fox, marten, carrion crow (Corvus corone), common buzzard (Buteo buteo) and ten scarcer raptor species.…”

“…One species with a significant conservation focus across Europe is the Western capercaillie. In Scotland, several well-funded conservation initiatives have failed to halt the pronounced decline of capercaillie since the 1970s, with evidence of a further 50% reduction from 2016 to 2020 and extinction being predicted within the next 50 years (Baines & Aebischer, 2023).…”

Evaluating diversionary feeding as a method to resolve conservation conflicts in a recovering ecosystem

“…Management includes intense culling of Cervidae (red and roe deer) to allow forest regeneration, and, unlike in more traditional neighbouring estates, there is no control of predators. The area encompasses the core of the remaining population of Scottish capercaillie (Baines & Aebischer, 2023).…”

“…One species with a significant conservation focus across Europe is the Western capercaillie (Tetrao urogallus) . In Scotland, several well-funded conservation initiatives have failed to durably halt the pronounced decline of capercaillie since the 1970s, with evidence of a further 50% reduction from 2016 to 2020 and extinction is predicted within the next 50 years (Baines and Aebischer, 2023). Climate change is the likely ultimate driver of decline through reduced food sources for chicks and hens (Wegge et al, 2022).…”

“…Lethal control of foxes and crows is common practice across many shooting estates in Scotland; even with this intervention, capercaillies have disappeared from all but a few shooting estates, with the core remnant populations now found in regions where predator control is not carried out (Baines and Aebischer, 2023). In contrast, two other potential grouse predators, badger ( Meles meles) and pine marten ( Martes martes, marten hereafter), are UK-protected species and cannot be routinely controlled in the same manner (MacPherson and Wright, 2021).…”