Investigating Associations Between Foraging Behavior and Blood Parasite Infection Risk in Birds

Birds in North America have been facing a decline in their populations (Rosenburg et al., 2019). One facet that has not been well-explored as an explanation to this problem is parasite prevalence. Parasites can have diverse and harmful effects on bird health (Alvardo-Piqueras et al., 2025; Martín-Maldonado et al., 2023). Bird life history traits, as well as parasite vector life history traits, can impact the prevalence of parasites within birds (Astudillo et al., 2013; McGregor et al., 2018) . This study focuses on the relationship between different bird species' foraging heights and niches and thier relationship to parasite prevalence.

Research Questions

How does parasite prevelence change between different foraging heights and niches a bird occupies?

Methods

Blood samples from 35 different species were collected from birds caught by the AREI banding station at Hueston Woods State Park in Ohio, USA. DNA was then extracted from these blood samples using QIAGEN DNeasy Blood & Tissue Kit. Nested PCR was then performed to test for the three genera of blood parasite (Plasmodium, Haemoproteus, and Leucocytozoon). The first set of external primers were HaemNF1 and HaemNR3. Internal primers were used to test for Plasmodium/Haemoproteus (HaemF, HaemR2) and for Leucocytozoon (HaemFL, HaemR2L).

Gel electrophoresis was then used to observe and identify positive and negative samples for each sample. The positive samples were collected and cleaned up using Wizard SV Gel and PCR Clean-Up System. The samples were then sent to be Sanger Sequenced to identify the species of parasite in each sample.

Data from Cornell Lab’s Birds of the World database was collected to determine the most commonly occupied foraging stratum of each bird species (Billerman et al. 2025). Determinations for foraging niches were obtained from the AVONICHE database (Sayol et al., 2026).

Foraging Niche Definitions

Table 1. Possible foraging niches of birds classified based on their foraging behaviors (Sayol et al., 2026).

Foraging Height Definitions

Table 2. Foraging Heights of birds and their classifications (Billerman et al., 2025).

35 different bird species were sampled and assigned to different foraging heights and niches. Each bird is placed on the picture at their assigned foraging height. Red represents high, blue represents mid, and yellow represents low. The colored circles assigned to each bird represents its foraging niche with purple as GEN, red as IGG, orange as IGE, and yellow as IVS.

Birds at Thier Assigned Foraging Heights and Niches

Figure 1. 35 different bird species were sampled and assigned to different foraging heights and niches. Each bird is placed on the picture at their assigned foraging height. Red represents high, blue represents mid, and yellow represents low. The colored circles assigned to each bird represents its foraging niche with purple as GEN, red as IGG, orange as IGE, and yellow as IVS.

Results and Discussion

There is a significant difference between infection prevalence and foraging height (Figure 2). Birds in the high foraging strata had a lower parasite prevalence than the low foraging strata (Figure 2).

When comparing individual parasite genera prevalence, there was no significant difference, suggesting other influences towards parasite prevalence. More than half of the birds that were classified as GEN or IGE were infected (Figure 4). Additionally, the generalist foraging niche had the most parasite diversity and was the only niche to have coinfection (Figure 4). The majority of birds classified as generalists are apart of the low foraging niche along with all birds classified as IGG (Figure 5). The high foraging height was the only strata to encompass the IVS foraging niche, which had no parasite infection (Figure 5).

Foraging Height vs. Overall Infection Prevalence

Figure 2. Overall parasite prevalence (including Leucocytozoon, Haemoproteus, and Plasmodium) in comparison to foraging strata using a 95% confidence interval for error bars. P-values of 0.000116 (Low), 0.1967 (Mid), and 0.01052 (High).

Parasite prevalence of each individual genera (Leucocytozoon, Haemoproteus, and Plasmodium) in comparison to foraging strata. Error bars were constructed with a 95% confidence interval.

Foraging Height vs. Haemoproteus Prevalence

Foraging Height vs. Plasmodium Prevalence

Foraging Height vs. Leucocytozoon Prevalence

Figure 3. Parasite prevalence of each individual genera (Leucocytozoon, Haemoproteus, and Plasmodium) in comparison to foraging strata. Error bars were constructed with a 95% confidence interval.

Number of individuals that have different parasite genera (plasmodium, Haemoproteus, or leucocytozoon), coinfection, or are uninfected compared to the foraging niche they occupy.

Number of Individuals vs Foraging Niche

Figure 4. Number of individuals that have different parasite genera (plasmodium, Haemoproteus, or leucocytozoon), coinfection, or are uninfected compared to the foraging niche they occupy.

Number of individuals that have a foraging niche of IGG (invertebrates glean ground),IGE (invertebrates glean elevated), IVS (invertebrates vertical substrate), or GEN (generalist) compared to the height they forage at.

Number of Individuals vs Foraging Height

Figure 5. Number of individuals that have a foraging niche of IGG (invertebrates glean ground), IGE (invertebrates glean elevated), IVS (invertebrates vertical substrate), or GEN (generalist) compared to the height they forage at.

Conclusions

Foraging height alone may not be enough to explain bird parasite prevalence. Considering a bird’s diet and feeding behaviors can provide a greater insight into parasite prevalence. Birds that are generalists feed on a much broader range of foods and therefore have a greater chance of parasite exposure. The low foraging height could encompass a lot of diversity in the food it offers, making parasite prevalence higher. Birds that are apart of the IVS niche (invertebrates vertical substrate), had no parasite infection at all and were additionally part of the high foraging group. From these results it can also be inferred that parasite vectors are also more concentrated at lower foraging heights.

The following is an image of poster presented at the 2026 Undergraduate Research Forum

Acknowledgements

Thank you to AREI and to the lab of Dr. Ashley Love for providing bird samples and banding data. We also thank the King family for their donation establishing the Applied Science Partnership Lab.

References

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NACE Career Readiness Competencies

Career + Self Development

I have broadened my involvement in scientific research through being part of my lab. This allowed me to grow the skills I need for graduate school.

Critical Thinking

Critical thinking had to be utilized during laboratory protocol such as troubleshooting when things have gone wrong. Additionally, it was used when compiling data and results to form a sound conclusion.

Technology

I learned and gained skills in technology such as using r coding software and excel.

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