DENSITY AND FORAGING ECOLOGY OF WOODPECKERS FOLLOWING A STAND-REPLACEMENT FIRE

Throughout its geographic range, the black-backed woodpecker (Picoides arcticus) is rare and appears very similar in its foraging ecology to 2 broadly sympatric congeners, the three-toed (P. tridactylus) and ha iry woodpecker (P. villosus). The purposes of our study were to test f or differences in foraging ecology of the black-backed, three-toed, an d hairy woodpeckers following a stand-replacement fire and to evaluate the importance of such fires to the viability of populations of the b lack-backed woodpecker. In boreal forests of Interior Alaska, endemic population densities of three-toed woodpeckers are low (<0.1/ha), and black-backed woodpeckers are extremely rare. Following the Rosie Creek fire near Fairbanks, Alaska, in June 1983, both species increased mar kedly. Densities of both species briefly exceeded 0.2/ha and remained high in a 67-ha plot at the edge of the burn during the following 2 ye ars. By December 1986, densities had declined to <0.1/ ha. Black-backe d woodpeckers fed primarily on charred portions of moderately to heavi ly burnt spruces and almost exclusively by excavating larval wood-bori ng beetles (Cerambycidae). Three-toed woodpeckers fed on less-burnt sp ruces and foraged in and immediately under the bark; bark beetle (Scol ytidae) larvae predominated in their diet. In contrast to earlier stud ies, our results demonstrate substantive differences in foraging sites , behavior, and diet of these 2 species. Foraging ecology of male hair y woodpeckers and black-backed woodpeckers, particularly females, was similar. In all 3 species, particularly the hairy woodpecker, females fed lower on trees and were far less numerous than males in the study area, which suggested intersexual displacement from foraging sites and habitats selected by males. In summer 1985, following initial adult e mergence of the 1983 cerambycid and scolytid cohorts, woodpeckers decl ined markedly and were absent by late spring 1986. Our results suggest the black-backed woodpecker is extremely specialized in its foraging niche, exploiting outbreaks of wood-boring beetles in dying conifers f or only 2-3 years after fires. Consequently, this species may be parti cularly vulnerable to local and regional extinction as fire suppressio n intensifies and programs of intensive salvage logging are pursued fo llowing fires.