Avian haemosporidian parasite prevalence and diversity in two populations of the American kestrel (Falco sparverius)

Parasite communities vary among host species and across space. However, little is known about differences in parasite communities between geographically and genetically distinct populations of the same host species. American kestrels (Falco sparverius) are small falcons with regionally distinct genetic populations across North America. We sampled kestrels from Delaware and Utah for avian haemosporidian parasites (genera: Haemoproteus, Plasmodium, and Leucocytozoon) and used molecular barcoding of the parasite cytochrome b gene (cyt b) to quantify parasite genetic lineage diversity. We identified four lineages of Haemoproteus parasites and one Leucocytozoon lineage infecting kestrels. A comparison with previous studies suggests that most of these lineages are largely restricted to kestrels. We found similar infection prevalence and lineage composition between the sites. All kestrels sampled in Utah were adults (i.e., sampled after hatch year), but in Delaware, we found adult birds had a higher infection prevalence than juveniles (i.e., hatch-year birds). Despite harboring largely the same parasite lineages, kestrels are unlikely to disperse between Utah and Delaware. The similarity in parasite lineages in the two kestrel populations could be due to a number of factors including broadly distributed vector species (of which little is known), movement of alternative and undetected host species, or transmission during migration or on overwintering grounds. Alternatively, the cyt b gene might not capture recent genetic differentiation among the parasites. Future studies should explore these various possibilities to understand the mechanisms underpinning parasite distributions across genetically structured host populations.