DIET OF NESTING SAVANNA SPARROWS IN INTERIOR ALASKA

Grasshopper populations on the Delta Agriculture Project area in inter ior Alaska exhibit a strong biennial periodicity (>25/m(2) in one year and <1/m(2) in the next). Savannah Sparrow (Passerculus sandwichensis ) stomach contents were examined during the breeding seasons over a 3- yr period. Grasshoppers constituted the largest portion (>45%) of the diet of adult Savannah Sparrows in the high grasshopper) years of 1990 and 1992. Beetles and hemipterans comprised the majority (66.5%) of t heir food in the low grasshopper year of 1991. Grasshopper presence in the diet varied in individual birds and among years. Occurrence in th e diet of other arthropod taxa was independent of year, but varied amo ng individuals. Almost no utilization of plant material was recorded. The results illustrate the responsiveness of breeding birds to a varia ble food supply and preference for highly nutritious grasshoppers when they are available.