Carry-Over Effects of Overwinter Climate and Habitat Productivity on Spring Arrival of Migratory Songbirds at a Northern Stopover Site
Horn, Lisa Christine
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Reduced rainfall in tropical regions may impact the ability of temperate-breeding songbirds to prepare for and execute their spring migration. I used 34 years of bird banding data from Ontario to test for the presence of climate-induced carry-over effects from wintering areas on the body condition and migration timing of birds en route to breed in Canada. Using linear models, I found that overwinter habitat productivity was significantly negatively influenced by the El Nio Southern Oscillation (ENSO) in the overwintering ranges in 3 of 7 species, where conditions were drier during El Nio years as expected. However, there was no consistent effect of ENSO or overwinter habitat productivity on stopover body condition or spring arrival date in southwestern Ontario. Widespread and long-lasting carry-over effects were not observed, suggesting that songbirds may compensate en route such that negative signatures from dry winters are absent late in migration.