Dispersal, Overwinter Mortality, and Recruitment of Spruce Grouse

Abstract

Dispersal and autumn to spring mortality of juvenile spruce grouse (C. c. franklinii) were studied in southwest Alberta [Canada] in 1970-1973. Changes in breeding population size primarily resulted from changes in numbers of yearlings recruited. Dispersal in autumn did not change the size or sex ratio of the juvenile cohort. The reduction in total juveniles during autumn and winter averaged 12%. Survival over winter for all age and sex classes averaged 88%. Of the loss of juveniles during autumn through spring, 90% was attributed to emigration, Among spring emigrants, known survival into summer was at least 64% and survival for 1 yr was at least 54%. Dispersal in spring was more variable than in autumn and was important for changing numbers of potential recruits. Density did not appear to affect the magnitude of dispersal.