In fact, it was concern over the condition of the bald eagle population that sparked researchers' interest in herons, according to Bob Anthony, leader of the Oregon Cooperative Wildlife Research Unit in OSU's Department of Fisheries and Wildlife. Anthony is Thomas' thesis advisor. Some eagle nests on this stretch of river have not produced any young for the past 19 years. Anthony wondered if there was another species they could monitor for environmental contaminants. For several reasons the research team looked to herons as that indicator species.
Herons are fairly common, with rookeries up and down the river.
Herons on the lower Columbia and Willamette do not migrate, so the residue in eggs is from local contamination. And, they are relatively insensitive to pollutants and are able to reproduce while carrying high contaminant loads. So in 1994, with a grant from the U.S. Fish and Wildlife Service, Carmen Thomas began the comprehensive research project, with Anthony as her advisor. It would be the basis for her master's thesis. During the next two years, she collected and chemically analyzed eggs and embryo liver tissue and observed heron behavior from birth to the fledgling stage of development, all in hopes of determining effects on herons and, ultimately, helping the bald eagle.