Movement of juvenile migratory birds from settlement to adulthood across the non-breeding range

  • Tómas Grétar Gunnarsson (Creator)
  • José A. Alves (Creator)
  • James Gilroy (Creator)
  • Boovar Porisson (Creator)
  • William J. Sutherland (Creator)
  • Peter M. Potts (Creator)
  • Jenny Gill (Creator)



Among migratory vertebrates, high levels of fidelity to non-breeding sites during adulthood are common. If occupied sites vary in quality, strong site-fidelity can have profound consequences for individual fitness and population demography. Given the prevalance of adult site-fidelity, the regions of the non-breeding range to which juveniles first migrate, and the scale of any subsequent movements, are likely to be pivotal in shaping distributions and demographic processes across population ranges. However, inherent difficulties in tracking migratory individuals through early life mean that opportunities to quantify juvenile settlement and movements across non-breeding ranges, and the mechanisms involved, are extremely rare.Through long-term, range-wide resightings of hundreds of colour-marked individuals from their first migration to adulthood, and application of state-space models, we quantify levels of juvenile and adult regional-scale movements and distances at different life stages across the whole non-breeding distribution range in a migratory shorebird, the Black-tailed Godwit (Limosa limosa islandica). We show that the probability of individuals changing non-breeding regions (seven historical wintering regions spanning the Western Europe range) at all ages are very low (mean movement probability = 10.9% from first to subsequent winter, and 8.3% from first adult winter to later winters). Movement between regions was also low between autumn and winter of the same year for both juveniles (mean movement probability = 17.0%) and adults (10.4%). The great majority of non-breeding movements from the first autumn to adulthood were within regions and less than 100 km. The scarcity of regional-scale non-breeding movements from the first autumn to adulthood means that the factors influencing where juveniles settle will be key determinants of non-breeding distributions and of the rate and direction of changes in distributions.
Date made available18 Jun 2024
PublisherDryad data repository

Cite this