Water level management and contaminant exposure to tree swallows nesting on the Upper Mississippi River

Environmental Monitoring and Assessment
By: , and 



The U.S. Army Corps of Engineers conducted a water drawdown on Navigation Pool 8 of the Upper Mississippi River during the summers of 2001 and 2002 to increase aquatic vegetation production and thereby improve fish and wildlife habitat. Flooding of previously dried wetlands, however, may increase the rate of mercury methylation and make mercury more available to terrestrial vertebrates that feed in aquatic environments. Our objective was to determine if mercury, other elements, and organochlorine contaminants were more available to vertebrates following the 2001 drawdown. Tree swallow (Tachycineta bicolor) eggs and nestlings were collected at two sites on Pool 8 and a nearby Reference site in 2000 (pre-2001 drawdown), 2001 (pre-2001 drawdown) and 2002 (post-2001 drawdown) and tissues were analyzed for mercury, other elements, and organochlorine contaminants. Bioindicator measurements of genetic damage, oxidative stress, ethoxyresorufin-O-dealkylase activity, and the ratio of liver to nestling mass were also measured in nestlings at all sites and all years. Based on a multivariate analysis, the 2001 drawdown of Pool 8 did not influence element concentrations, organochlorine concentrations, or bioindicator response. Concentrations of inorganic and organochlorine contaminants in tree swallow eggs and nestlings were not at toxic levels. Hatching success did not differ among years and was comparable to the nationwide average.
Publication type Article
Publication Subtype Journal Article
Title Water level management and contaminant exposure to tree swallows nesting on the Upper Mississippi River
Series title Environmental Monitoring and Assessment
Volume 133
Issue 1-3
Year Published 2007
Language English
Contributing office(s) Patuxent Wildlife Research Center
Description 335-345
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Environmental Monitoring and Assessment
First page 335
Last page 345
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