Seasonality and causes of black grouse (Lyrurus tetrix, Galliformes, Tetraonidae) death in Western Russia according to count of remains

Abstract

Black grouse (Lyrurus tetrix) death in north and middle zones of the Russian plain were studied in 1981–2013 according to counts of the remains of perished individuals. The average annual death of birds older than 1.5–2 months is estimated as 2.0–2.5 birds/km2. Its maximum falls into spring or winter-spring season and minimum into summer. Predation is main cause of death; all other reasons (unusual weather, hunting, no established circumstances) determine only one-quarter of total loss. Raptors cause maximal death of black grouse in northern regions. No significant differences between death of males and females were detected, but seasonal patterns of their death is not the same, and factors that determine their act differently. The female losses as a result of activity of all predators are distributed relatively uniformly by seasons; male death is higher in spring than in other times of year. The dynamics of male and female removal by only raptors is similar: maximum in spring, decrease in summer, and drop to minimum in autumn and winter. Seasonal distribution of losses due to activity of carnivorous beasts is uneven; male death is higher in transitional seasons (as compared with winter and summer), and female losses are maximal in winter and minimal in spring-summer period.