The Influence of Spring Snow Depth on White-Tailed Ptarmigan Breeding Success in the Sierra Nevada

The relationship between spring snow depth and breeding success of an introduced population of White-tailed Ptarmigan (Lagopus leucurus altipetens) in the Sierra Nevada, California, was studied from 1982 through 1987. Yearly spring snow depth varied from 50.8 cm to 424.2 cm. Hatch dates were later in years of deep snow (P < 0.05) but brood size showed no relation to snow depth. Nesting success, chick survival, and brood success (all of which contribute to breeding success) were negatively correlated with snow depth as was breeding success (P < 0.05). The number of paired ptarmigan in the study area varied from 22 (in 1987) to 46 in 1985 which was the year with the least snow; however, no significant relationship existed between breeding numbers and snow depth. Successful reproduction of White-tailed Ptarmigan in the Sierra Nevada appears to be strongly affected by snow, potentially due to its influence on the availability of resources such as nest sites, food, and cover.