Dispersal in a patchy landscape reveals contrasting determinants of infection in a wild avian malaria system

1. Understanding exactly when, where and how hosts become infected with parasites is critical to understanding host-parasite coevolution. However, for host-parasite systems in which hosts or parasites are mobile (for example vector-borne diseases), the spatial location of infection, and the relative importance of parasite exposure at successive host life-history stages, are often uncertain. 2. Here, using a six-year longitudinal dataset from a spatially referenced population of blue tits, we test the extent to which infection by avian malaria parasites is determined by conditions experienced at natal or breeding sites, as well as by postnatal dispersal between the two. 3. We show that the location and timing of infection differs markedly between two sympatric malaria parasite species. For one species (P. circumflexum), our analyses indicate that infection occurs after birds have settled on breeding territories, and because the distribution of this parasite is temporally stable, hosts co...