Abstract: The migration to northern latitudes of North America by neotropical songbirds may overlap with the phenology of their caterpillar food resources (i.e. lepidopteran larval eclosion and development) in temperate forest stopover habitats. However, there is growing evidence that the phenology of these localized food resources is responding to the warming of regional and global temperatures. In northern latitudes, this change is even outpacing other areas of the globe. This may have important implications for songbirds whose migration from the tropics is initiated by photoperiod whereas the emergence of lepidopteran larvae and their leafy hosts are synchronized with accumulating spring warmth. Using migration records from various spring surveys at Urbana, Illinois, I assembled a 100-year data set of wood warbler arrival times and peak migration dates. I compared these dates to local accumulated growing degree days (GDD; base 5° C) for their caterpillar food resources: 150 GDD coincides with 50% egg eclosure), 200 GDD with 80-100% egg eclosure), and at 300 GDD signifies the beginning of the spring peak in larval activity. During two consecutive springs in Urbana, Illinois, I censused a well-studied stopover habitat, monitoring the daily population of warblers along 3000 meters of transects, the weekly caterpillar population on 6000 canopy leaves, and the weekly the phenological stage of 300 trees in the forest canopy. In an average spring I found a significant overlap between the percent of forest trees in the leaf growth stage, number of caterpillars per leaf, and warbler species richness (p=0.01). However, over the last 100 years there has been no relationship among accumulating spring temperatures, peak warbler migration, or arrival date for individual warbler species and in some years the conditions for peak larval activity precedes peak warbler migration by nearly a month. Moreover only two (yellow-rumped warbler and ovenbird) of the eight wood warbler species investigated show a significant trend toward early arrival at the stopover (p < 0.05). These results contradict hypotheses that all flora and fauna will adjust to global warming. The full impact of early springs on migrant songbird populations remains unknown, yet these results herald the dangers that mismatches in the synchrony of this tritrophic system due to global warming may further stress declining populations of neotropical migrant songbirds.