Prevalence and diversity of malaria parasites (genus Plasmodium) in the imperiled Saltmarsh Sparrow are greater at northern sites.

This article investigates the prevalence, diversity, and geographic variation of malaria parasites (genus *Plasmodium*) infecting the endangered Saltmarsh Sparrow (*Ammospiza caudacutus*) across its breeding range along the U.S. Atlantic Coast. Screening 280 individuals via polymerase chain reaction (PCR), the study found a 17% overall infection rate with six distinct *Plasmodium* lineages, noting higher prevalence and parasite diversity at northern latitudes. Although mercury is a known immunosuppressant and the Saltmarsh Sparrow exhibits high mercury exposure, no significant association was detected between blood mercury levels and malaria infection status in this study. The findings highlight the importance of prioritizing northern populations of this coastal specialist for conservation and pathogen monitoring, considering geographic variation in disease risk and environmental factors.