Environmental contaminants and nesting behavior of great blue herons from the Columbia and Willamette Rivers, Oregon and Washington
Thomas, Carmen M.
Anthony, Robert G.
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Reduced productivity and elevated contaminant concentrations have been documented in fish-eating birds, including bald eagles, from the Columbia River since 1984. To determine whether nest attendance was related to contaminant concentrations in eggs of fish-eating birds, we e"xamined breeding behavior of great blue herons at six colonies, in Oregon and Washington. We chose great blue herons as an indicator species for the effects of environmental contaminants on the guild of fish-eating birds because previous studies have demonstrated their utility. Patterns of attendance and nest visitation were significantly different among sites. The site with the highest concentrations of p,p'-DDE and total PCBs had significantly lower nest attendance relative to the reference site. Differences in nest attendance among colonies were inversely related to p,p'-DDE and PCB concentrations; however fledging and reproductive success in all colonies were similar to those reported for healthy populations. Differences in nest attendance and visitation among sites did not appear to be affecting nestling survival pre-fledging