Age-dependent timing and routes demonstrate developmental plasticity in a long-distance migratory bird

1. Longitudinal tracking studies have revealed consistent differences in the migration patterns of individuals from the same populations. The sources or processes causing this individual variation are largely unresolved. As a result, it is mostly unknown how much, how fast, and when animals can adjust their migrations to changing environments. 2. We studied the ontogeny of migration in a long-distance migratory shorebird, the black-tailed godwit (Limosa limosa limosa), a species known to exhibit marked individuality in the migratory routines of adults. By observing how and when these individual differences arise, we aimed to elucidate whether individual differences in migratory behaviour are inherited or emerge as a result of developmental plasticity. 3. We simultaneously tracked juvenile and adult godwits from the same breeding area on their south- and northward migrations. To determine how and when individual differences begin to arise, we related juvenile migration routes, timing, an...