Breeding origins and pattern of migration of Bluethroats Luscinia svecica wintering from Iberia to Senegal as revealed by stable isotopes

Capsule: Stable isotope analyses reveal some degree of migratory connectivity of Bluethroat populations wintering from Iberia to West Africa. Aims: To identify the probable breeding origins of Bluethroats wintering from Iberia to Senegal. Methods: Bluethroat feathers (P1) were sampled from individuals at their wintering areas. These feathers were then analysed for stable H isotopes (delta H-2). We assigned individual Bluethroats to approximate geographic origin using likelihood-based assignment procedures. Results: We observed spatial segregation between different Bluethroat populations. At wintering sites north of the Sahara Desert, Bluethroats wintering to the west came from further west origins than those which overwintered to the east. Bluethroats from central-eastern Europe overwintered either within the circum-Mediterranean region or in Senegal. We found no clear evidence supporting a sub-Saharan wintering range for birds breeding in Iberia (Luscinia svecica azuricollis subspecies). Conclusion: North of the Sahara Desert, we found what might be a parallel migration pattern. The apparent lack of Luscinia svecica namnetum Bluethroats in Senegal suggests to some extent some kind of leap-frog migration between some Luscinia svecica cyanecula populations and the L. s. namnetum subspecies.