Habitat requirements of birds should be considered when planning silvicultural activities. Thus, we studied the use of forest resources by brown creepers (Certhia americana) and red-breasted nuthatches (Sitta canadensis) for 1 year in 8 forest stands on the western slope of the Sierra Nevada to determine the causes of temporal and spatial patterns in resource use. Both species used stands with a diverse structure characteristic of mature mixed-conifer forests. Intensity of stand use by both creepers and nuthatches was correlated (<tex-math>$r_{s}=0.81-0.86$</tex-math>, P < 0.05) with the percent basal area of sugar pine (Pinus lambertiana) over all sample periods. Creepers used incense cedar (Calocedrus decurrens) more than any other tree species throughout the year, and foraged more (P < 0.05) on incense cedar in January-February than in spring and summer. Nuthatches were more varied in their use of tree species, and spent more (P < 0.05) time on California black oak (Quercus kelloggii) in May-June than in September-October. Creepers foraged almost exclusively on tree trunks, whereas nuthatches used a greater variety of substrates and foraging modes. Density of bark-surface arthropods varied among tree species, sample periods, and forest stands. Incense cedar had the highest arthropod density throughout the year. Arthropod density was negatively correlated (<tex-math>$r_{s}=-0.15$</tex-math>, P < 0.05) with trunk diameter for all tree species. However, no statistically significant relationships between arthropod density and bird foraging behavior or stand use were detected. Our results indicate that resource managers should maintain a diversity of stand structure and species compositions to meet year-round habitat requirements of bark-foraging birds in the Sierra Nevada.
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