Differential survival throughout the full annual cycle of a migratory bird presents a life‐history trade‐off (Buechley et al., 2021)

Long-distance migrations are physically demanding, and understanding the costs and benefits of this behavior is key to ecology and evolution. A hypothetical migration cost should be balanced by higher productivity or survival, but few studies directly quantify survival patterns throughout the year and across a species' range. Using telemetry data from 220 migratory Egyptian vultures (Neophron percnopterus), tracked for 3,186 bird-months across 70% of their global range, we tested survival differences during the annual cycle. We estimated monthly survival probabilities relative to migration and latitude using a multi-event capture–recapture model, considering age, origin, subpopulation, and uncertainty from tracking data. We found lower survival during migration (β = −0.816) and higher survival on non-breeding grounds at southern latitudes (<25°N; β = 0.664) compared to breeding grounds. Survival was also higher for individuals from Western Europe (β = 0.664) and increased with age (β = 0.030). Anthropogenic causes accounted for half of the known mortalities, mostly in northern latitudes. Many juveniles drowned in the Mediterranean during their first autumn migration, while few mortalities occurred in the Sahara, suggesting species-specific migration barriers. Our study advances the understanding of migration’s fitness trade-offs. Although migration is associated with lower survival, this is likely offset by higher survival on non-breeding grounds at lower latitudes. Increased anthropogenic mortality in northern areas could disrupt this balance. Future research on migration’s benefits, such as productivity across latitudes, could provide insights into migration evolution and its persistence in a changing world.

· Enlace https://doi.org/10.1111/1365-2656.13449

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Ayuda PTR2022-001249 financiada por:

UNION EUROPEA - FONDO EUROPEO DE DESARROLLO REGIONAL

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Differential survival throughout the full annual cycle of a migratory bird presents a life‐history trade‐off (Buechley et al., 2021)