The effects of wind and fuel stores on stopover departure behavior across a migratory barrier

During annual migrations between breeding and nonbreeding grounds, billions of land birds encounter migratory barriers en route. Although birds are thought to be more selective (i.e., cross under favorable wind conditions) and spend more time refueling at stopover sites when confronted with these barriers, there is no direct evidence to support these hypotheses. Using 2 automated radio-telemetry arrays at stopover sites situated before (south of) and after (north of) a large ecological barrier (Lake Erie), we tracked departure decisions of American redstarts Setophaga ruticilla and yellow-rumped (myrtle) warblers Setophaga coronata coronata during spring migration. We found evidence that condition, age, and tailwind assistance were all positively correlated with the likelihood of departure. Interestingly, these patterns did not differ between species, with presumably differing migratory tactics, nor across sites, suggesting that during spring migration, migratory songbirds may follow general rules for departure from stopover sites, despite varying ecological and life-history contexts.