A preliminary assessment of mercury in the feathers of migratory songbirds breeding in the North American subarctic
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A preliminary assessment of mercury in the feathers of migratory songbirds breeding in the North American subarctic I. J. Stenhouse
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E. M. Adams1 L. M. Phillips2 S. Weidensaul3 C. L. McIntyre4 ●
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Accepted: 24 August 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Passerines appear to have a greater sensitivity to mercury than other avian orders, and little data exists for mercury exposure in songbirds breeding at high latitudes. In this preliminary study, we examined mercury exposure in 12 migratory songbird species breeding in Denali National Park & Preserve, in subarctic interior Alaska. Overall, we analyzed 343 feather samples collected in 2015–2017 for their total mercury content. Mercury levels found in feathers indicates exposure during the period of feather growth, which we assume largely took place on the breeding ground. In this limited sample of songbird feathers, mercury concentrations ranged from near zero to 6.34 μg/g. Most species sampled showed relatively low mercury, but some individuals had high enough concentrations to be subject to adverse physiological and behavioral effects. There was an indication that mercury concentrations of breeding songbirds may vary by diet composition, with non-invertivorous species possibly tending towards lower mercury concentrations. Overall, however, the degree of mercury exposure observed was low for songbirds breeding in the subarctic. Further examination would prove useful in clarifying mercury exposure and ecological relationships in this under-studied region. Keywords Songbirds Mercury Feathers Subarctic Alaska ●
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Introduction As a well-known environmental contaminant, mercury (Hg) poses a significant threat to wildlife species that are exposed to it through their diets (UNEP 2013). Human-sourced Hg emissions are highly mobile in the Earth’s atmosphere, can travel enormous distances, and can be deposited in remote areas, such as polar regions and northern boreal forests (AMAP 2011, UNEP 2013, AMAP/UNEP 2015). Under specific conditions, Hg can be converted by bacteria into methylmercury (MeHg), a highly toxic form that readily biomagnifies up through the food web (Wiener et al. 2003, Rimmer et al. 2010, Lavoie et al. 2013). Dietary exposure to
* I. J. Stenhouse [email protected] 1
Biodiversity Research Institute, Portland, ME, USA
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National Park Service, Denali National Park & Preserve, Denali Park, AK, USA
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Milton, NH, USA
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National Park Service, Denali National Park & Preserve, Fairbanks, AK, USA
Hg has significant impacts on the health of birds (Scheuhammer et al. 2007). Susceptibility to disease (Hawley et al. 2009, Lewis et al. 2013, Henry et al. 2015), an impaired physiology (Herring et al. 2012, Maddux et al. 2015), and the development of aberrant behaviors (Hallinger et al. 2010, Kobiela et al. 2015), for example, can result in reduced reproductive success in songbirds (Jackson et al. 2011, Varian-Ramos et al. 2014, Ackerman et al. 2016), while dec
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