The objective of this project is to use tree swallows (Tachycineta bicolor) to understand the ecological risk posed by per- and polyfluoroalkyl substances (PFAS) at selected Department of Defense (DoD) sites in the mid-Atlantic region of the United States. This study will fill data gaps on effects of PFAS on birds, especially those with high exposure potential, like aquatic insectivores. This project will include delineation of exposure pathways and quantifying effects, if any, on ecological receptors.

Technical Approach

Tree swallows are widely used to quantify distribution and effects of local surface water and sediment contamination. Study populations can be established at specific locations of interest by deploying nest boxes in suitable habitats. Because tree swallows feed near those nest boxes (within 400 meters (m) of emergent aquatic insects), residues in their tissues reflect sediment contamination for bioavailable chemicals of concern. Additionally, data are now available on exposure and effects of various chemicals of concern, including PFAS, in tree swallows at more than 100 locations across North America.

A Tree Swallow in the Mid-Atlantic

Tree swallow nest boxes will be deployed in proximity to suitable habitats at up to three DoD locations in the mid-Atlantic area. DoD locations will include former Naval Air Station (NAS) Joint Reserve Base Willow Grove, where swallow work is ongoing, and possibly Patuxent River NAS in Maryland and Joint Base McGuire in New Jersey. As nesting is being initiated, nest boxes will be visited regularly and reproductive data collected. Reproductive data will include the number of eggs laid, number of eggs that hatched, and number of fledglings. Reproductive data will be compiled using estimates of daily nest and egg survival. At appropriate times, a sample of eggs will be collected and analyzed. A few nestlings will be collected from each nest box for analytical chemistry and a suite of bioindicator responses such as ethoxyresorufin-o-deethylase (detoxifying liver enzyme), thyroid hormone levels, oxidative stress measurements, and genetic damage assessments among others.


This study is scalable, and no-observed-adverse-effect level/lowest-observed-adverse-effect level (NOAEL/LOAEL) results are transferable to other DoD locations. The results will allow the DoD to further understand the ecological risk posed by PFAS to avian species in the mid-Atlantic region of the United States. Results will contribute to assessments of the health of the target ecosystems and will provide a baseline for future trend and/or geographic analyses at DoD locations. (Anticipated Project Completion - 2024)