Variations in wing morphology among subspecies might reflect different migration distances in Bluethroat

Abstract

Long-distance migrants have a more pointed and concave wing than short-distance migrants. These pointed and concave wings are thought to minimize the energy-cost of flight. Detailed analyses of wing morphology among populations might therefore offer clues about the migratory behaviour of those populations whose wintering areas are not known. In this work we analysed variations of wing shape of three populations of Bluethroats (Luscinia svecica) from western Europe with different migration distances: L. s. namnetum (breeds mainly in W France, winters in W Portugal and Morocco, n = 31), L. s. cyanecula from central Europe (breeds in C Europe, winters in S Europe and N and C Africa, n = 182), L. s. cyanecula from Iberia (breeds in Iberia, but their wintering areas are still unknown, n = 39). To assess wing morphology we used C2 and C3 wingtip shape indices proposed by Lockwood et al. (1998), measuring wing pointedness and convexity, respectively. Males had more pointed and concave wings. As expected, namnetum was found to have a relatively more rounded wing than cyanecula, as well as a more convex wing, agreeing with the fact that namnetum moves shorter distances between its breeding and wintering areas. No significant differences were observed between cyanecula from C Europe and Iberia. Our results suggest that Bluethroats from Iberia are long-distance migrants.