Breeding dispersal of Baltic dunlins is not an adaptive response to unpredictable nest flooding

Human-driven habitat loss and climate change are rapidly degrading bird breeding grounds worldwide. For ground-nesting waterbirds using low-lying shore habitats, combined pressures of predation, intensified flooding, and vegetation overgrowth can drastically reduce reproductive success. In East Bothnian Bay, flood-related nest losses of the Baltic dunlin (Calidris alpina schinzii) have drastically increased over the past two decades (from 10 % to 46 %), compounding the primary threat of nest predation. Breeding dispersal, the decision to return to or relocate from a previous nest site, may offer a behavioral response to such threats. Using long-term reproductive data from 184 individuals over 20 years and multivariate generalized linear mixed models, we examined local (within-site) between-year dispersal in relation to nest fate, its relation to flooding , and tested whether dispersal distances influence subsequent reproductive success. We found that between-year dispersal tended to be higher following nest failure, particularly in males. However, males that experienced flooding did not show consistent nest relocation away from the shoreline, and dispersal distances had negligible effects on daily nest survival the following year. Our results suggest that Baltic dunlins relocate regularly within their breeding site, but dispersal is influenced by individual variation and nest fate rather than as an adaptive response to environmental threats. These findings suggest that threatened bird populations may be unable to cope with environmental change and are therefore more likely to face extinction without further conservation management.