HABITAT USE AND POPULATION CHARACTERISTICS OF THE WHITE-TAILED PTARMIGAN IN THE SIERRA-NEVADA, CALIFORNIA

We studied an introduced population of White-tailed Ptarmigan (Lagopus leucurus) during 1987 and 1988. Ptarmigan colonized alpine habitat 79 km north and 114 km south of their release site within 18 years of their liberation in the Sierra Nevada, California. Population densities were the lowest reported for the species. However, sex and age ratios were similar to native populations. Breeding season habitats were in areas of tall (>30 cm) willow (Salix) shrubs and contained more subshrub, moss, and boulder cover than in unused habitats. In the postbreeding season, ptarmigan used topographic depressions within breeding territories; brooding hens used moist meadows, while flocks occupied sites with abundant boulders. Ptarmigan primarily used the Salix anglorum antiplasta vegetation alliance on rocky, north-facing slopes. Willow abundance and proximity to water were the most discriminatory variables in logistic regression analyses between habitats used and unused by ptarmigan during the breeding and postbreeding seasons.