The prevalence and intensity of Infection with isosporan Coccidia parasites in wild passerine birds varies greatly between bird species. Faeces of Infected hosts contain oocysts that are a source of new infections when ingested. As a consequence, we expect that the main route of coccidiosis transmission in the wild is related to the foraging behaviour of the hosts, and that bird species are exposed to infective oocysts, depending upon the way of foraging. We studied how prevalence and intensity of isosporan infection in wild birds are related to foraging stratum, gregariousness, and diet. Our data reveal that a bird's feeding habits play a significant role in the extent and severity of infection by isosporan Coccidia in the wild.