Data from: Generational shift in spring staging site use by a long-distance migratory bird

In response to environmental change, species have been observed altering their migratory behaviours. Few studies, however, have been able to determine whether these alterations resulted from inherited, plastic, or flexible changes. Here we present a unique observation of a rapid population-level shift in migratory routes — over 300 km from Spain to Portugal — by continental black-tailed godwits Limosa limosa limosa. This shift did not result from adult godwits changing staging sites, as adult site use was highly consistent. Rather, the shift resulted from young godwits predominantly using Portugal over Spain. We found no differences in reproductive success or survival among individuals using either staging site, indicating that the shift resulted from developmental plasticity rather than natural selection. Our results therefore suggest that new migratory routes can develop within a generation and that young individuals may be the agents of such rapid changes.

The data package contains 8 files:
- Data on adult staging site use
- Data on staging site use young
- Data on parent-offspring pairs (table S2)
- Data on brood success of females in the Haanmeer polder
- Data on brood success of males in the Haanmeer polder
- Data on proportion resighted in Spain (Figure S1A)
- Data on resighting proportion in Portugal (Figure S1B)
- Data for subsequent juvenile survival analysis