Abstract: Migration is an ecological phenomenon driven by multiple factors, among which parasite infection has recently gained increasing attention and is becoming a research hotspot. Using Haemosporidia and their avian hosts as a model system, we examined the complex interaction mechanisms and coevolutionary relationships between parasite infection and migration. On one hand, migratory birds are exposed to higher infection risk from haemosporidian parasites, due to their utilization of diverse habitats, high-density aggregations, and immune suppression, which facilitates transmission and geographical spread of the parasites. On the other hand, severely infected individuals may die during migration, and chronically infected individuals can recover in parasite-free areas. Birds can therefore mitigate infection risk by migrating away from high-prevalence areas. Furthermore, haemosporidian infection can influence the phenology of migratory birds, including departure and arrival times, by interfering with energy allocation. From an evolutionary perspective, haemosporidian infection acts as a selection pressure which shapes the evolution of avian migration strategies. Conversely, bird migration drives speciation and local adaptation of Haemosporida by expanding their geographical ranges, providing opportunities for host switching, and imposing periodic selective pressure. Current research still faces challenges regarding long-term field tracking and mechanistic verification. Future studies may integrate omics analyses, novel monitoring technologies, and manipulative experiments to gain an in-depth understanding of bird migration-parasite interactions and coevolution under global change.

Key words: parasite, migratory exposure, migratory escape, immune trade-off, host switching