Element concentrations in tree swallows (Tachycineta bicolor) from the U.S. and Binational Great Lakes’ areas of concern

Selected elements were targeted in state Remedial Action Plans as one group of chemicals affecting the Beneficial Use Impairments of Great Lakes Areas of Concern (AOC). Livers of nestling tree swallows, Tachycineta bicolor, were harvested from 76 sites in the Great Lakes which included multiple sites at 27 AOCs and 12 reference sites from 2010 to 2015 and analyzed for 21 elements. Mercury concentrations were at background levels at all sites. Elevated cadmium (Cd) concentrations were associated with industry. The highest Cd values were from the Black River, OH AOC and associated with historic coke production, but were not at toxic levels. Lead (Pb) concentrations were highest on the Rouge River, MI AOC, the oldest and most heavily populated and industrialized area in southeast Michigan. Individual lead Pb concentrations were elevated to a level associated with delta-aminolevulinic acid dehydratase inhibition, but not to a level considered toxic. In contrast, livers harvested from sites on the southwest shore of Lake Michigan had selenium concentrations elevated to levels associated with reduced avian reproduction. One likely source of the high Se concentrations was pollution from a local coal-fired power plant. Concentrations of the remaining elements were at background levels.