Seasonal and Geographic Variation in the Foods of Adult White-Tailed Ptarmigan

Weeden, Robert

Crops of 167 White-tailed Ptarmigan collected in 23 localities from Colorado to Alaska were examined during this study. The leaves of Salix and Ranunculus, Dryas flowers, grass and sedge seeds, and Polygonum fruits were common items in the scattered spring and summer collections available. White-tailed Ptarmigan in Colorado ate Salix leaves, Draba fruits, and Polygonum fruits early in September, shifting to Salix buds and twigs and Dryas leaves later in September and October. No berries were found in autumn crops of White-tailed Ptarmigan from Colorado, although fruits of Empetrum nigrum and Vaccinium spp. were eaten by this bird in the fall in various parts of Alaska and British Columbia. Colorado ptarmigan apparently subsist mostly on Salix buds and twigs in winter. No Alnus or Betula was found in crops of white-tails from this state. In contrast, Alnus catkins make up an important part of the winter diet of Alaskan white-tails, with Salix and Betula of lesser importance. The difference in winter diet between white-tails from Colorado and Alaska may be due to an increased proportion of Alnus in northern winter ranges, and to competition for fairly restricted food supplies among the three species of Lagopus in Alaska.

Seasonal and Geographic Variation in the Foods of Adult White-Tailed Ptarmigan

Series