If you build it, will they stay? Using passerine nestlings as bioindicators of heavy metal accumulation at a former brownfield site

Background/Question/Methods Soils of brownfield sites are notoriously laden with heavy metal pollutants that may have adverse effects on resident wildlife. Previous studies at our study site, Liberty State Park in Jersey City, NJ, have shown high levels of lead (Pb) and zinc (Zn) in the soil, and that these metals are translocating to plant tissue where they become available to the greater food web. This site is unique as it offers more than 200-acres of assembled natural habitat in an extremely dense urban setting, offering what seems to be ideal nesting habitat for avifauna. But are these soil contaminants “poisoning” the avifauna that feed and nest at the site and creating a population sink? We used nestlings as bioindicators to evaluate if an abandoned, naturally recolonized browfield site is able to support sustainable bird populations. Analyzing bird feathers is an effective and non-invasive method to measure bioaccumulation of heavy metals. Since nestlings are fed food sources taken near the nest, testing nestling feathers can result in a clear indication of a site's heavy metal pollutants. During this study we collected feather samples from 65 nestling house wrens (Troglodytes aedon) and 41 nestling American robins (Turdus migratorius). Additionally, we collected samples from 35 house wren nestlings at a control site, located in rural New Jersey that has no history of pollutants. Metal concentrations in feather samples were determined using a plasma-atomic emission spectrophotometer (ICP-AES). Results/Conclusions Our results indicate that concentrations of Pb, chromium (Cr), and arsenic (As) at the study site were significantly higher than those found at the control site. However, there was no significant difference with Zn or iron (Fe) between the control and study sites. While these levels were high at the control site they were still well below clinical levels known to have adverse physiological or neurological effects. We found little intra-clutch variability within our samples, but significant inter-clutch variability, indicating that metal levels found in an entire brood of nestlings have a negative relationship to their proximity to areas of higher soil concentrations. Our results also indicate that there was no temporal change in metal concentrations comparing nestlings from first clutches to those of second clutches, indicating that metal concentrations remain relatively constant during the course of the breeding season. Overall, our study indicates that nestling passerines could effectively be used as bioindicators of heavy metal accumulation to help evaluate the viability of brownfield habitat.