Migratory birds rely on stopover sites in order to refuel during their journeys. Birds will spend a few days at these sites until they have enough fat stores built up in order to fly again towards their destination. These sites, however, expose them to a number of challenges, such as parasite infection. This thesis focuses on one type of avian blood parasite that may chronically infect birds at their stopover sites, Haemosporidian parasites (also known as avian malaria.) Prior research on other bird species has found that infection may cause birds to arrive later at stopover sites, have reduced reproductive success, and poor body condition. Yet, the effect on immune function has been shown to be varied.

Parasite presence was investigated in two related thrushes: Swainson’s Thrush (Catharus ustulatus), a long distance migrant, and Hermit Thrush (Catharus guttatus), a short distance migrant. Both of these species migrate through Amherst, Massachusetts, however, they may respond differently to parasite infection due to their differing migration strategies. By quantifying presence/absence of avian malaria in each bird and analyzing the relationship between parasite presence, immune function, and arrival date, we can gain a greater understanding of the effect of these parasites and how it may differ based on long or short-distance migration strategy.