Associations Between Nest Characteristics and Avian Blood Parasite Prevalence and Diversity

Avian malaria, caused by genera such as Plasmodium, Haemoproteus, and Leucocytozoon, is an important contributor to bird population declines alongside other environmental stressors. Infection risk is largely influenced by exposure to vectors such as mosquitoes, black flies, and biting midges. This study investigates how nest characteristics, including height, type, and habitat, influence parasite prevalence and diversity. We predicted that nests with greater exposure to vectors, specifically those that are lower, open, and located in riparian habitats, would exhibit higher infection rates.

Bird blood samples were collected during Fall 2025 at the Avian Research and Education Institute (AREI) station in Hueston Woods, Ohio. DNA was extracted from all samples and analyzed using nested PCR to detect parasite DNA, followed by gel electrophoresis to determine infection status. Positive samples were purified and sequenced using Sanger sequencing to identify parasite lineages. Each species was categorized by nest type (open-cup, cavity, or dome), habitat (riparian, mesic, or variable), and nest height based on species-specific ranges from established literature. Statistical analyses, including Welch’s t-tests, chi-square tests, and regression models, were used to evaluate relationships between nesting variables and infection prevalence.

This study shows that nest height and habitat are key ecological predictors of avian malaria risk, with increased exposure to vectors leading to higher infection rates. These findings emphasize the importance of environmental conditions in shaping disease dynamics in bird populations. However, limitations such as small sample sizes in certain categories and the observational nature of the study restrict causal conclusions. Future research should expand sample sizes, include seasonal variation, and incorporate direct measurements of vector abundance to better understand the mechanisms driving infection patterns.

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• Cornell Lab of Ornithology, 2024. All About Birds; ​

• Billerman et al., 2020. Birds of the World, Cornell Lab of Ornithology; ​

• National Audubon Society, 2024. Audubon Guide to North American Birds;