Capercaillie Tetrao urogallus in Scotland - demography of a declining population.

Abstract

Capercaillie Tetrao urogallus numbers declined in Scottish forests between 1992 and 1997, although the rate (mean 16% per year, 95% CL I-30%) differed among forests. Hens declined more quickly than cocks despite the sex ratio in chicks favouring females. A probable explanation is that adult cocks lived longer. Juvenile survival was less than adult survival, largely because juveniles were more likely to die from hitting fences. Although poor reproduction was probably the main cause of the decline, this might not have occurred had fence strikes been substantially fewer.