Effects of food availability on the distribution of migratory warblers among habitats in Jamaica

1. Theoretical arguments suggest that distributions of migratory birds in w inter should match patterns of food availability, but in reality the match between migrants and their food may be imperfect because, for various reaso ns, birds may be unable to 'track' food resources. We tested the hypothesis that food availability influences the distribution of migratory canopy-for aging insectivorous warblers wintering in Jamaica. 2. Over a wide spatial scale (24 sites on the island), warbler abundance va ried significantly among sites and habitats and was significantly dependent on measures of arthropod biomass. Alternative factors (vegetation characte ristics, resident bird competitor abundance, predator abundance) were not c orrelated with warbler abundance. 3. Over a short temporal scale (about 2 weeks) at a single site, warbler ab undance increased as predicted quantitatively after a natural, rapid increa se in arthropod biomass. 4. Over a longer temporal scale (the duration of a winter), changes in dens ity and persistence of individually marked American redstarts (Setophaga ru ticilla, L.) on six sites corresponded with concurrent fluctuations in arth ropod biomass. 5. These results document a strong association between arthropod biomass an d warbler abundance in time and space, suggesting that warblers wintering i n Jamaica distribute themselves in response to food resources. 6. We hypothesize that dominance hierarchies and variable movement strategi es operate in concert with birds' responses to food to influence the distri bution of wintering warblers at different spatial scales. Whether food avai lability determines habitat quality remains to be investigated.