Michel Leconte

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

ABSTRACT 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 (δ2H). 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.

Migratory Connectivity in European Bird Populations: Feather Stable Isotope Values Correlate with Biometrics of Breeding and Wintering Bluethroats Luscinia svecica

Summary. Understanding the migratory connectivity of migrant species is fundamental to their effective conservation. Analysis of individual traits that can vary geographically, such as biometrics and stable isotopic values of tissues, can help establish migratory connections. The bluethroat Luscinia svecica is a species of conservation concern in Europe (Annex I Birds Directive). Our aim was to identify the possible migratory connectivity of bluethroats Luscinia svecica breeding in central and western Europe (subspecies L. s. namnetum, L. s. azuricollis and L. s. cyanecula in part) with their wintering areas in southern Europe and Africa using biometric and stable isotopic (&dgr;2H) analyses. Overall, the morphological and stable isotopes analyses provided two clusters of localities, one for the Atlantic French, Portuguese and Moroccan localities, corresponding to the breeding and winter quarters of L. s. namnetum, and another for the remaining localities (Spain, The Netherlands, Germany and Senegal), corresponding to the ranges of L. s. azuricollis and L. s. cyanecula. Migratory connectivity of L. s. namnetum is strong but it is much weaker for the other two subspecies. Biometric data were positively correlated to the stable isotope values, suggesting that the results derived from both methodological approaches lead to similar conclusions.