Migratory connectivity and temporal segregation of dunlin (Calidris alpina) in Portugal: evidence from morphology, ringing recoveries and mtDNA

Abstract

Migratory connectivity plays an important role in conservation of long-distance migrant birds. Here, we study migratory links of dunlin (Calidris alpina), focusing on a stopover and wintering region (Portugal) where it is known that migration routes of dunlin from a broad geographic range (three subspecies) converge, and populations occur simultaneously or separated in time. We combine three methods (ringing recoveries, morphometrics and molecular genetics) to assess breeding origins and extent of temporal segregation of dunlin assemblages. Ringing recoveries show temporal separation of dunlin from different migration routes. Birds found in Portugal during August and September, migrating via Britain, reveal links to breeding areas in Iceland and Greenland. In October, a clear shift to more eastern migration routes occurs, with most Portuguese winter records from stopover sites along migration routes of populations from northern Scandinavia and Russia. Mitochondrial DNA (mtDNA) of Portuguese dunlin was compared with breeding populations. Spring and autumn migrants in Portugal corresponded to C. a. schinzii and C. a. arctica populations, while the Portuguese winter population clearly differs by including mtDNA haplotypes of C. a. alpina. For genetically sexed individuals, we found significant differences in morphology (bill and tarsus length) supporting the temporal separation of populations/subspecies revealed by recoveries and mtDNA. Our results give evidence for migratory connectivity of dunlin populations between geographic areas previously not considered connected. They confirm the existence of clear differences in breeding origin between birds in Portugal at different times of year. These results are important in the consideration of future long-term conservation plans.