Oregon Junco Foods in Coniferous Forests

Abstract

A food analysis was made from the gizzard contents of 262 Oregon juncos (Junco oreganus) collected in western Oregon from 1954 through 1962. The average annual diet was about half seed and half insect material. Juncos ate the seeds of many plants and also some germinants (sprouting seeds, and seedlings with seed coat on the cotyledons); those of Douglas-fir (Pseudotsuga menziesii), blackberry and raspberry (Rubus spp.) and hawkweed (Hieracium albiflorum) were the most important. A great variety of insects was taken but ants (Formicidae), snout beetles (Curculionidae), ground beetles (Carabidae), and leafhoppers (Cicadellidae) comprised the greatest volume. Douglas-fir seeds and germinants were an important sought-after junco food averaging 12%. They represented a trace in seed failure years, 6% in light seed years, and 32% in moderate to heavy seed years. Hemlock (Tsuga spp.) averaged only 1% of the food, even though it was a consistent seed producer. Seeds of redcedar (Thuja plicata) were not taken. Destruction of Douglasfir seeds and germinants by juncos should be considered when evaluating factors that may hinder regeneration. The authors were Wildlife Research Biologists, Denver Wildlife Research Center, Bureau of Sport Fisheries and Wildlife, U. S. Department of Interior. Their present respective addresses are: Bureau of Sport Fisheries and Wildlife, P. 0. Box 1208, Bend, Oregon 97701; and Rocky Mountain Forest and Range Experiment Station, Forest Service, U. S. Department of Agriculture, P. 0. Box 3313, Laramie, Wyoming 82070. They would like to thank Melva C. Gashwiler for her assistance in collecting the juncos and recording field data. The work of Malcolm H. Zirges, Department of Fisheries and Wildlife student at Oregon State University, who helped to compile the data, is also appreciated. Walter G. Dahms and James W. Barrett. of the Pacific Northwest Forest and Range Experiment Station, and Ann H. Jones and Robert B. Finley, Jr., of the Denver Wildlife Research Center kindly reviewed and edited the manuscript.