Connecting the Wintering and Breeding Sites of Migratory Songbirds Using New Isotopic and Genetic Methods

Scientists and birdwatchers alike have noted precipitous population declines in many species of migratory songbirds during the last thirty years. However, the transitory nature of migratory birds makes it difficult to pinpoint the exact cause of these declines. Some postulate that habitat loss on the tropical wintering grounds is the cause, while others suggest that forest degradation on the temperate breeding grounds may be negatively influencing reproductive success. Songbirds are also undoubtedly affected by disturbances along the migratory pathway at the many stopover sites upon which they depend. Without the ability to relate specific breeding and wintering populations and their associated migratory routes, developing effective management strategies remains elusive. Historically, efforts to correlate breeding, wintering, and migratory populations have relied on large-scale banding programs. However, these efforts have generally met with limited success because recapture of banded birds, especially on their wintering grounds, is rare.