DOWN LOGS AS HABITAT FOR FOREST-DWELLING ANTS - THE PRIMARY PREY OF PILEATED WOODPECKERS IN NORTHEASTERN OREGON

Logs on the forest floor in 240 sample plots in the Blue Mountains of northeastern Oregon were counted and their physical characteristics de scribed in relation to ant colonization. The plots were located in 12 home ranges of pileated woodpecker (Dryocopus pileatus (L.)), a Manage ment Indicator Species in USDA Forest Service management guidelines. O ne or more species of ants were found in 62% of 1,385 sectioned logs. Of 13 species of ants found, the most common were Lasius alienus (Foer ster), Formica neorufibarbis Emery, and Camponotus modoc (Wheeler). Wo od-dwelling ants that colonize down logs and snags are the primary pre y for pileated woodpecker. Relationships between physical characterist ics and species of down logs, their colonies of ants, and foraging pil eated woodpeckers are discussed. Differential occurrences among genera and species of ants suggest a complex picture of species, sizes, and stages of decay of logs chosen for colonization. The relationships of logs and ants to management of pileated woodpecker and to western spru ce budworm (Choristoneura occidentalis (Freeman)), a major forest-defo liating insect, are also explored.