Songbird Exposure to Mercury

A White-crowned Sparrow sings in Denali National Park and Preserve.

NPS/Ken Conger

Little is currently known about the level exposure to mercury encoutered by migratory songbirds. While songbirds are more sensitive to mercury than other birds, high-latitude migrants have not been widely studied. This study looked at mercury exposure in 12 migratory songbirds breeding in Denali National Park and Preserve. Most species sampled showed low levels of mercury in their feathers, but some individual birds had high enough mercury concentrations that they may show physiological or behavioral impacts.

A preliminary assessment of mercury in the feathers of migratory songbirds breeding in the North American subarctic

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.

Stenhouse, I. J., E. M. Adams, L. M. Phillips, S. Weidensaul, and C. L. McIntyre. 2019. A preliminary assessment of mercury in the feathers of migratory songbirds breeding in the North American subarctic. Ecotoxicology DOI 10.1007/s10646-019-02105-2.