Winter Habitat Relationships of Blue Grouse on Hardwicke Island, British Columbia

Abstract

Winter habitat of radio-tagged and color-banded blue grouse (Dendragapus obscurus) was studied on Hardwicke Island, British Columbia, Canada. Western hemlock (Tsuga heterophylla) was the dominant tree at 94% of all sites where grouse were observed in winter; snow and a variety of shrubs, herbaceous plants and mossess were dominant forms of ground cover. Hemlock and Douglas-fir (Pseudotsuga menziesii) needles made up most of the winter food. Habitat tolerances of blue grouse were broad. Radio-tagged juveniles were found in successional stages ranging from 4 to >250 years in age that supported trees from 1 m to >60 m in height. Mature forest (>250 years old) was preferred winter habitat, early successional stages (.ltoreq.20 years in age) were used frequently, and mid-successional stages (21-100 years in age) were less frequently used. Juveniles wintered at higher elevations and closer to breeding range than expected by chance with juvenile males wintering at higher elevations than juvenile females. Habitat preferences of a small sample of radio-tagged adults were similar to juveniles. A sample of nonradioed grouse of all ages indicated that males and females wintered at different elevations, on average, and may have used different successional stages. There were no differences in habitat use by adults and juveniles of a given sex. Mortality of grouse living in early successional stages was high in fall but after fall migration, survival did not seem to be influenced by habitat.