Contaminant exposure of tree swallows, Tachycineta bicolor, nesting in 27 Areas of Concern (AOC) in the Great Lakes' basin was assessed from 2010 to 2014 to assist managers and regulators in their assessments of Great Lakes AOCs. Contaminant concentrations in nestlings from AOCs were compared to nestlings from nearby non-AOC sites. Polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) concentrations in tree swallow nestling carcasses at 30% and 33% of AOCs were below the mean concentration for non-AOCs. Polycyclic aromatic hydrocarbon (PAH) concentrations in nestling stomach contents and perfluorinated compound (PFC) concentrations in nestling plasma at 67% and 64% of AOCs were below the mean concentration for non-AOCs. Concentrations of PCBs in nestling carcasses were elevated at some AOCs, but were modest compared to highly PCB-contaminated sites where reproductive effects have been documented. Concentrations of PAHs in diet were sufficiently elevated at some AOCs to elicit a measurable physiological response. Among AOCs, the PFC compound perfluorooctane sulfonate concentrations in plasma were the highest on the River Raisin, MI (geometric mean 330 ng/ml), but well below an estimated toxicity reference value (1,700 ng/ml). Both PAH and PCB concentrations in nestling stomach contents, and PCBs in carcasses, were significantly correlated with concentrations in sediment reported in another study, thereby reinforcing the utility of using tree swallows to assess bioavailability of sediment contamination. This article is protected by copyright. All rights reserved.