Explaining variation in Colorado songbird blood mercury using migratory behavior, foraging guild, and diet
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Explaining variation in Colorado songbird blood mercury using migratory behavior, foraging guild, and diet Carley J. Knutsen1 Claire W. Varian-Ramos ●
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Accepted: 23 November 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Methylmercury is a contaminant of growing global concern that has been shown to accumulate in a variety of taxa, including songbirds. Birds in the same area can accumulate mercury to strikingly different levels. While diet and trophic level clearly play an important role in mercury bioaccumulation and biomagnification, other factors including foraging guilds and migratory behavior may influence mercury levels as well. Here we examine interspecific variation in blood mercury levels in songbirds living in the Fountain Creek watershed on the Front Range of Colorado. We found that the species with the highest mercury had blood mercury concentrations over 75 times higher than the species with the lowest levels. Carnivores had the highest blood mercury levels, but ground foraging and long distance migration also were correlated with higher mercury concentrations. This information may shed light on what species are most at risk from mercury pollution and help to target conservation resources at contaminated sites. Keywords Bioaccumulation Blood mercury Interspecific variation Methylmercury Passeriformes ●
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Introduction Environmental contaminants pose a serious conservation challenge due to their harmful effects on wildlife. Pollutants in animals have been linked to reduced growth and survival (Gilbertson et al. 1991; Mac and Edsall 1991; Varanasi et al. 1993), changes in behavior (Hecnar 1995), and also impaired reproduction (Gilbertson et al. 1991) leading to reduced fitness and potential population declines. Interspecific variation in contaminant levels has been found, even among similar species (Borrell 1993; Jackson et al. 2011, 2015; Rimmer et al. 2005; Ma 1989; Townsend et al. 2013; Tsipoura et al. 2008). Multiple heavy metal contaminants were found to vary significantly among species of wild songbirds (Tsipoura et al. 2008). Moreover, Tsipoura et al. did not observe any consistent patterns for metal concentrations being higher in any one of the songbird species (2008), suggesting that animal species have unique bioaccumulation for different contaminants. This large
* Claire W. Varian-Ramos [email protected] 1
Biology Department, Colorado State University–Pueblo, 2200 Bonforte Blvd., Pueblo, CO 81001, USA
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amount of variation among similar species makes it vital to understand interspecific variation, especially when broadly applying the results of ecotoxicological research. In this study, we focus on the effects of behavior and diet on interspecific variation in mercury accumulation among songbird species. Mercury is a contaminant of concern for songbirds, and interspecific variation in bioaccumulation has been found (Rimmer et al. 2005; Jackson et al. 2011, 2015; Townsend et al. 2013; Tsipoura et al. 2008). Biomagni
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