The use of foraging sites by a foliage- and bark-gleaning guild of insectivorous birds was studied for 2 yr in a California oak woodland. Choices of plant type, perch size, and foraging height are presented for both residents and migrants in two contrasting seasons (fall/winter and spring). Seasonal differences were fewer than differences between years at the same season. Niche breadths and overlaps of residents in the 2nd yr of the study were mostly larger in spring than in fall/winter, although the contrasts were not statistically significant. The niche breadth findings are viewed as consistnt with a prediction of optimal foraging theory that a broader range of patch types will be used when food is abundant. Dendrograms based on niche overlaps for fall/winter and spring showed that three resident species constituted the core of the guild, together with two migrants in fall/winter one in spring.