Intra-African bird migration: Identifying contrasting patterns of connectivity in widely distributed species

Migration strategies within the tropics are poorly understood as are the drivers of movement and the degree of connectivity between sites in migrant birds that have their global range and life cycle exclusively on a single continent. Migratory connectivity between populations may be affected by past climatic fluctuations as well as contemporary threats that affect habitat connectivity resulting in genetic differentiation. Here, integrated molecular and morphological data was used to examine genetic diversity, elucidate patterns of differentiation and assess evolutionary history of western, eastern and southern African populations of African pygmy kingfisher (Ispidina picta), woodland kingfisher (Halcyon senegalensis) and Diederik cuckoo (Chrysococcyx caprius). Our results provided evidence of genetic lineages corresponding to subspecies designation for all three species. Lack of differentiation was observed within subspecies of African pygmy kingfisher and Diederik cuckoo, indicating that connectivity between populations has been maintained. However, genetic substructure was evident within woodland kingfisher with three distinct genetic clusters for birds from Ghana, Gabon and Uganda. Morphometric variation was identified between subspecies. We additionally detected a continental gradient in wing length from western to the eastern populations of woodland kingfisher as well as sexual dimorphism within I. p. natalensis. Here, we recommend that this or similar approaches be applied to other widespread African bird species that are often overlooked in a global conservation context. We further suggest that future conservation strategies should potentially focus on ensuring that connectivity between populations of migrant birds is maintained on the African continent.