You are what you eat: urban soil lead predicts American robin (Turdus migratorius) blood lead in Flint, MI

Abstract

High levels of pollutants can occur in urban environments and pose a threat to human residents as well as local wildlife. Many urban centers suffer from lead-contaminated drinking water due to the corrosion of pipe infrastructure. Irrigation with this water may contribute to soil lead levels. The American robin (Turdus migratorius) is a widespread songbird in North America, well-known for hunting earthworms in urban lawns. This earthworm specialization results in the ingestion of large amounts of soil. This study investigates the impact of the Flint, Michigan (MI) water crisis, during which the city water supply was contaminated with lead, on American robins during their breeding season in southeast MI. We compared soil lead levels (SLL) and blood lead levels (BLL) of birds captured at irrigated sites of Flint to those captured at non-irrigated sites of Flint during April - August from 2018 to 2020. Control sites included irrigated sites in a nearby city without a known history of lead pollution (Ypsilanti, MI: irrigated urban control) and non-irrigated rural sites. BLL were elevated in irrigated sites of Flint relative to the irrigated urban control and non-irrigated rural sites. Further, robin BLL were positively and strongly correlated with lawn SLL across our seven study sites suggesting that high BLL in American robins may predict elevated soil lead levels. Further research should address how lead might be impacting urban wildlife and if robins can serve as a bioindicator of lead exposure for other neighborhood inhabitants, including human children whose main route of lead exposure is through soil contact.