Weights of Ontario spruce grouse by sex, age, and breeding success

Abstract

Weights of spruce grouse (Canachites canadensis) captured or shot in northeastern Ontario, mainly during the spring and summer of 1979–1982, are described and related to sex, age, with or without brood, and weights from other North American populations. Spruce grouse from Ontario are among the lightest in weight, but follow the general trend of lowest weight in spring and summer to highest weight in winter. During spring and summer, females lost proportionately more weight than males, suggesting that the reproductive period was more stressful for females. Males weighed least in May and June, and adults weighed more than yearlings. Adult females weighed more than yearlings in May. Females were lightest in June and July when females with chicks weighed less than those without. Adults gained weight earlier after their chicks hatched than yearlings, and more adults had broods. Among broodless hens, yearlings lost weight, but weights of adults were relatively stable. From a variety of comparisons, some yearling hens were at times in poor condition relative to adults.