Use of Stable Isotopes (δ13C and δ15N) to Infer Post-breeding Dispersal Strategies in Iberian Populations of the Kentish Plover (<em>Charadrius alexandrinus</em>)

Beaches are among the habitats most frequented by migratory birds for breeding and/or wintering. However, threats such as human pressure and sea level rise can reduce the availability of these habitats for different species. The presence of alternative areas, such as salt pans and brackish habitats, is essential for many migratory shorebird populations. This study addresses the post-breeding dispersal of the Kentish plover (Charadrius alexandrinus) in the Iberian Peninsula by analysing C and N isotopes in feathers. The study was conducted at six locations along the Iberian coast, which were categorized in three areas: NW Atlantic coast, the Atlantic coast of Andalusia and the Mediterranean coast. Although linear mixed models did not reveal any significant effects of sex or coastal area on isotopic levels, the variability in the data suggests different habitat-use strategies in the post-reproductive period. Birds from the northwest of the Iberian Peninsula exhibit greater fidelity to a single habitat type, i.e. coastal beaches, while populations from the Mediterranean coast and the Atlantic coast of Andalusia show different individual dispersal strategies, occupying coastal habitats and freshwater wetlands. The lack of alternative habitats for the northwest Iberian population, the reduction in available habitat due to rising sea levels and human pressure together pose a serious threat to the survival of this species, already with an unfavourable conservation status.