Although migrant songbird populations are highly dependent on winter conditions, little research has been conducted during this time of year. Previous research has focused on habitat, food and competition within species, while largely ignoring competition with other species. I am testing the hypothesis that American Redstarts (Setophaga ruticilla) compete for food (insects) with Adelaide’s Warblers (Dendroica adelaidae) in southwest Puerto Rico.
Results/Conclusions

Results to date suggest that redstarts and Adelaide’s are competing: they feed in the same places using the same methods, insect densities decline sharply over the winter with concurrent declines in body condition of both species, and the two species are aggressive towards each other. The foraging niche of Adelaide’s does not appear to shift after redstarts leave, and their territories overlap in two dimensions, suggesting that Adelaide’s are superior competitors that force redstarts to use a vagrant fugitive strategy.