For many migratory avian species there is a short period of time when conditions are suitable for reproduction. Many bird species face spatial and temporal changes in food availability during the breeding season. This study assessed temporal changes in foraging, food abundance, and nestling trophic position of a model migratory species, the Black-throated Blue Warbler (Dendroica caerulescens, Gmelin). Black-throated Blue Warbler diet is composed mostly of Lepidoptera larvae. Stable isotope analysis and a Bayesian isotope mixing model were used to estimate nestling diet composition and temporal dietary changes. Proportion of larvae in nestling diet decreased in nestlings hatched later in the breeding season. In addition to assessing nestling diet, adult male Black-throated Blue Warblers foraging choices were assessed. Male tree foraging tree species preferences did not change during the breeding season. This study provides evidence that temporal changes affect nestling diet composition, but do not affect male foraging tree species preference.