Natural Variation In Malarial Infection And Immune Investment In A Migratory Songbird, And The Effects Of Infection On Flight Performance

Endurance flight and immune defense are energetically costly activities for birds, and there may be a trade-off between migration and immune investment. Avian blood parasites consume host resources, which may decrease a bird’s resource pool so that endurance flight and immune defense may not be possible simultaneously. I developed a molecular method to detect and quantify blood parasite infection in migrating yellow-rumped warblers (Setophaga coronata), and measured immune activity. I assessed the impact of infection on endurance flight performance and refueling in captive birds. Infection status was not related to age or sex, or timing of migration, and haptoglobin decreased with capture date during autumn migration. Spring relapses in infection were seen in captive birds, and no effect of infection status on flight performance or refueling was evident. My results suggest that warblers are well adapted to malarial parasites, and may facilitate the spread of disease across large geographic distances