The objective of the proposed study is to evaluate the exposure of a healthy population of water-associated bird species to per- and polyfluoroalkyl substances (PFAS). We will evaluate if modeling risk from PFAS in bird eggs and fish, combined with existing laboratory-derived toxicity reference values (TRVs), reflects ongoing field monitoring, which indicates these birds are not significantly impacted by PFAS. The project team will focus on bird species at a high trophic level, with high site fidelity, and that forage within a small range during nesting. Eggs will be selected from breeding piscivorous birds such as grebes or common loons. The study will build upon the SERDP-funded project ER21-3464 and the needs identified in Conder et al. (2021) on field ecology studies. Specifically, it will evaluate the accuracy of existing PFAS TRVs with a population of healthy birds.

The proposed approach uses two distinct technical tasks to assess PFAS toxicity to birds from analyzing PFAS in eggs of up to four species of aquatic birds representing three feeding guilds (i.e., omnivores, invertivores, and piscivores) and prey tissue samples. PFAS analyses will be conducted on egg samples from up to four bird species. Egg samples will be from water-associated bird species that are: (1) high on the food chain, (2) have high site fidelity and (3) forage within a small range during nesting. Homogenized whole-body composite fish tissue and benthic invertebrate samples co-located in space and time with a subset of the egg samples will also be analyzed. Homogenized whole egg PFAS concentrations will be compared to laboratory-determined egg PFAS TRVs to field-validate the existing TRVs. Fish and benthic invertebrate PFAS concentrations will be incorporated into existing dietary risk models, including from previous and ongoing SERDP projects, to evaluate laboratory-determined dietary PFAS TRVs. Risk conclusions determined using laboratory-determined PFAS TRVs will be compared to field monitoring conclusions that breeding bird populations of the study species are healthy.

The project will aid the understanding of PFAS presence and transport within aquatic ecosystems and re-emphasize the ecological health of local bird populations over laboratory/model predicted health. Results will aid risk assessments and provide insights for Department of Defense (DoD) facilities. Basic questions that may be answered include whether PFAS are detectable in available egg tissue samples indicating maternal transfer and if PFAS are detectable in the main dietary items of nesting birds. If PFAS are detected in tissue samples, this study will look for changes in concentrations of eggs associated with changes in dietary items of breeding birds with varied diets. The proposed research is expected to show that eggs of selected bird species are an effective method of monitoring exposure and assessing the potential adverse population-level effects on birds. Results from this study will be transferable to other DoD locations where PFAS are expected to be present. (Anticipated Project Completion – 2024)