Nutrition of Willow Ptarmigan in Northern Alaska

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Abstract
Analyses of crop contents of 540 willow ptarmigan (Lagojms lagopus) collected in the Brooks Range of northern Alaska showed that in winter, the birds depend on the buds and twigs of willow (Salix spp) for their nutrition. Up to 94% of the diet is willow and 80% may be of a single sp. (S. alaxensis). Birds wintering in the southern part of the Brooks Range use more buds and catkins of dwarf birch (Betula glandulosa). During fall and summer, herbaceous plants, berries and willow leaves are eaten. Birch has a higher caloric value than willow at any season. The caloric content of willow buds remains constant in winter but rises in spring prior to catkin flowering. The caloric content of the average diet remains nearly constant throughout the winter, but drops in summer due to the use of herbaceous plants and berries which have lower caloric equivalents than buds. Birds wintering in the south of the range consume a diet higher in caloric value due to inclusion of large amounts of birch and aspen (Populus tremuloides). Willow ptarmigan are well adjusted to derive their nutrition from a number of sources but prefer willow when it is readily available.

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