Mercury in Sharp-Tailed Sparrows Breeding in Coastal Wetlands.

Current levels of anthropogenic mercury (Hg) in the environment can cause harm to humans and wildlife. Well-documented negative effects on birds are described, but there is presently limited information for passerine exposure to mercury. Some investigations have used insect-eating birds as potential bioindicators of mercury exposure. However, our understanding of methlymercury (MeHg) availability to birds in coastal wetlands, tidal systems that may be especially conducive to Hg methylation, remains poor. Two species of sharp-tailed sparrow breed in coastal wetlands in eastern North America and are suitable candidate indicators for contaminants in these habitats. We measured blood Hg from breeding Saltmarsh (Ammodramus caudacutus) and Nelson’s (Ammodramus nelsoni) sharp-tailed sparrows in five Maine salt marshes to determine if these species could be used to assess the extent of MeHg availability in salt marshes. Blood Hg for both species differed among the five marshes with concordance between species and site such that marshes with high MeHg levels were the same for both species. Blood Hg levels were 1.7 times higher in Saltmarsh sharp-tailed sparrows than in Nelson’s and exceeded Hg levels from passerines in known MeHg-contaminated lakes. This research is the first to show that insectivorous passerines breeding in salt marshes are accumulating MeHg. [ABSTRACT FROM AUTHOR]