Plumage color and reproductive output of eastern bluebirds (Sialia sialis) nesting near a mercury-contaminated river

Abstract

Despite the growing evidence of mercury's impact on ecosystems, few studies have looked at the environmental impact of mercury pollution on terrestrial songbirds and the complex ways through which mercury might influence their fitness. In 2007–2008 eastern bluebirds (Sialia sialis) were monitored on mercury contaminated and reference sites for blood and feather mercury, reproductive success and plumage coloration. Higher tissue mercury accumulation was associated with plumage that was overall brighter and shifted towards the UV portion of the spectrum. In females, long-term mercury exposure, as indicated by feather mercury, was associated with smaller clutches of eggs. In males, recent mercury exposure, as indicated by blood mercury, was associated with a reduction in the proportion of hatchlings that fledged, potentially through reduced male provisioning of offspring. Reproductive success and plumage color are closely linked in bluebirds through mate choice, and our findings indicate that mercury contamination is associated with reproductive success directly and possibly indirectly, through coloration of bluebirds.