Nesting Parameters of Blue Grouse and Their Relevance to Populations

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Abstract
Data on clutch size, fertility and hatchability of eggs, and nesting success were obtained from 136 nests of blue grouse [Dendragapus obscurus] during 9 yr of studies on Vancouver Island, British Columbia, Canada. Only clutch size differed significantly between yearling and adult females, with yearlings having the smallest clutches. This difference between age classes is likely related to physiological maturity of the 2 groups of females. Clutch size varied among years but these variations showed no relation to subsequent breeding density. Fertility of eggs was high in all years (95-100%) but did show some significant differences among years. Hatchability of fertile eggs was high (97.3%) and constant among years. Nesting success showed one significant difference among years but this had no apparent effect on subsequent breeding density. Overall, the parameters measured were relatively constant among years and deviations that did occur bore no relationship to breeding density in the following year. None of the 4 variables examined were significantly different between a period of relatively low and stable population density and a period of increasing and higher population density. Hence, no variations were necessary in any of the parameters examined to bring about population change. Fertility, gross hatchability and hatchability of fertile eggs only were all lower in an aviary than in eggs left in the wild. Nevertheless, fertility and hatchability were comparable to those reported for aviary studies of other species of galliforms, both domestic and wild.

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