Foraging substrate use of American Three-toed Woodpeckers ( Picoides dorsalis ) in white spruce-dominated forests of the Black Hills of South Dakota

Isolated, sedentary species with low population densities are at increased risk of population declines because of habitat disturbances relative to common, widely distributed species. The American Three-toed Woodpecker (Picoides dorsalis) population in the Black Hills of South Dakota is of conservation concern because of its geographic isolation, sedentary behavior, and association with relatively small, patchily distributed, white spruce (Picea glauca) habitats. The presence of sufficient suitable foraging habitat may positively affect fitness in birds, but because few foraging studies exist for American Three-toed Woodpeckers, and none have occurred in the Black Hills, understanding foraging habitat needs is critical for management and conservation planning for this isolated population. During the breeding seasons of 2006–2008 we recorded foraging observations of American Three-toed Woodpeckers in the Black Hills and examined foraging substrate preferences by comparing foraging substrate use to availability using initial and sequential observations of individual focal birds. We found that American Three-toed Woodpeckers foraged on large living and dead white spruce and large ponderosa pine (Pinus ponderosa) trees in higher proportion than their availability and on small living spruce and pine in lower proportion than their availability. Foraging event durations were longer on large spruce snags than on other tree species, size, and status (living or dead) categories. These results suggest that mature white spruce forests, and especially those with large living and dead white spruce trees, are important foraging habitats for the American Three-toed Woodpecker during the breeding season in the Black Hills. Recent proposed, but subsequently withdrawn, forest management plans that would have reduced white spruce forest extent in the Black Hills would likely have negative impacts on foraging resources for this bird species of regional conservation concern.