Mercury concentrations in eggs of red-winged blackbirds and tree swallows breeding in Voyageurs National Park, Minnesota

Archives of Environmental Contamination and Toxicology
By: , and 

Links

Abstract

Most investigations of the environmental effects of mercury (Hg) have focused on aquatic food webs that include piscivorous fish or wildlife. However, recent investigations have shown that other species, including passerine songbirds, may also be at risk from exposure to methylmercury (MeHg). We quantified Hg concentrations in eggs of two species of songbirds, red-winged blackbirds (Agelaius phoeniceus) and tree swallows (Tachycineta bicolor), nesting in Voyageurs National Park, Minnesota, USA. Geometric mean concentrations of total Hg (THg) were lower in red-winged blackbird eggs [218 and 107 ng/g dry weight (dw) for 2012 and 2013, respectively] than in tree swallow eggs (228 and 300 ng/g dw for 2012 and 2013, respectively), presumably reflecting differences in the trophic positions of these two species. Concentrations of MeHg averaged 98.4 % of THg in red-winged blackbird eggs. Levels of THg observed in this study were well below critical toxicological benchmarks commonly applied to eggs of avian species, suggesting these breeding populations were not adversely affected by exposure to MeHg. In red-winged blackbirds, concentrations of THg in eggs collected in 2012 were twice those in eggs collected in 2013. Hg levels in eggs of both species increased with date of clutch initiation. In red-winged blackbirds, for example, temporal patterns showed that a 3-week delay in clutch initiation increased egg THg by 60 %. These observations indicate that in ovo exposure of wetland birds to MeHg can vary significantly within nesting season as well as between years.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Mercury concentrations in eggs of red-winged blackbirds and tree swallows breeding in Voyageurs National Park, Minnesota
Series title Archives of Environmental Contamination and Toxicology
DOI 10.1007/s00244-016-0263-y
Volume 71
Issue 1
Year Published 2016
Language English
Publisher Springer
Contributing office(s) Contaminant Biology Program, Upper Midwest Environmental Sciences Center
Description 10 p.
First page 16
Last page 25
Country United States
State Minnesota
Other Geospatial Voyageurs National Park
Online Only (Y/N) N
Additional Online Files (Y/N) N