Haemoproteus infection status of collared flycatcher males changes within a breeding season.

In ecological studies of haemosporidian parasites, prevalence is typically considered as a stable attribute. However, little is known about the possible within-host dynamics of these parasites that may originate from environmental fluctuations, parasite life cycles and the ability of hosts to suppress or clear infection. We sampled the blood of male collared flycatchers Ficedula albicollis twice within a breeding season and investigated the determinants of initial infection status and change in infection status. We found that older males tended to be initially more infected at courtship. Change in infection status was unrelated to male traits, but a widespread disappearance of Haemoproteus pallidus infection from the blood was detected between courtship and nestling rearing. The probability of change in infection status increased with the time elapsed between sampling occasions. This suggests that the disappearance of infection from the blood was due to either an active parasite suppression mechanism or the beginning of the latent phase in the parasite life cycle. Initial infection status or disappearance of infection from the blood showed no correlation with breeding success. These results show that H. pallidus infection status and thus prevalence are dynamically changing attributes and this has widespread practical and ecological implications.