Effects of Avian Malaria in a Population of Cerulean Warbler (Setophaga Cerulea) With First Documentation of Haemosporidian Lineages Infecting the Species.

Avian haemosporidians (Haemosporida) commonly infect terrestrial birds worldwide and can have negative consequences for individuals. We studied avian haemosporidian infections and mitochondrial cytochrome-b lineages in a southern Indiana breeding population of cerulean warbler (Setophaga cerulea; n = 51) over 2 yr with traditional microscopy and standard molecular methods. We investigated potential effects of infection on individual body condition, associations of host specificity and levels of infection (parasitemia) according to haemosporidian lineage genus, and geographic distributions of lineages. Additionally, we aimed to provide the first documentation of haemosporidian lineages for the species and to estimate population prevalence and parasitemia for comparison with earlier studies of the species. Parasitemia was low (<1% of cells infected) for most individuals, indicative of chronic infections, and we did not find any negative effects of infection on body condition of males (n = 49); however, mean body condition of individuals with Plasmodium sp. infections was higher than that of uninfected individuals, which could reflect survivorship bias in the sample. Neither host specificity nor parasitemia varied by haemosporidian genus, and for some lineages, we inferred likely geographic regions of transmission to Neotropical-Nearctic migrants, including the cerulean warbler. Prevalence was moderate at 31.4% across both years, and we documented 11 unique lineages in the genera Haemoproteus and Plasmodium, 2 of which were novel. These findings advance knowledge of host-parasite interactions for a declining avian species and add to the broader field of avian haemosporidian biology, including novel host-parasite associations.