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Assessing the effects of legacy contaminants on egg and nestling survival of tree swallows in Great Lakes Areas of Concern
Citation:
Etterson, M., C. Custer, T. Custer, AND P. Dummer. Assessing the effects of legacy contaminants on egg and nestling survival of tree swallows in Great Lakes Areas of Concern. SETAC North America, Orlando, FL, November 06 - 10, 2016.
Impact/Purpose:
not applicable
Description:
Great Lakes Areas of Concern (AOCs) are affected by many stressors, some of which are environmental contaminants including PCBs, PBDEs, persistent organochlorine pesticides, dioxins, benzenes, and other chemicals. These toxicants can accumulate in aquatic biota and ultimately transfer to insectivorous birds that use the aquatic areas within AOCs. We used a relatively new multistate survival modeling approach to examine the relationship between avian egg and nestling survival and 11 contaminant concentrations in representative eggs of Tree Swallows (Tachycineta bicolor) using nest boxes placed near reference (n=10) and contaminated sites (n=59) around the Great Lakes. A total of 1,303 nests and 7,752 eggs were included in the modeling effort. Our analyses controlled for other common sources of variation in egg survival, including female age, date within season, year, and both site and AOC. Site, date within year, year, and female age all proved to be important variables in explaining egg survival. Among environmental contaminants, we found few associations between egg and nestling failure and contaminant concentration in representative eggs. Total dioxin furan toxicity equivalents (TDFTEQ) was significantly positively associated with egg failure, but significantly negatively associated with nestling death. Across the full dose response for this contaminant, empirically observed values of TDFTEQ were concentrated at the low end, with only a few values at the higher end of the dose-response. Site, as an explanatory variable, proved much more valuable, as judged by AICc, than AOC, suggesting that sites within AOC can vary considerably in stressors and/or response to stressors. Overall, concentrations of the 11 contaminants examined here, appear to be at concentrations low enough to cause few problems for Tree Swallow reproductive success.