Mercury linked to ‘dramatic’ decline of migratory songbirds in North America

New findings from Western University support the scientific opinion that mercury is one of the determining factors for the dramatic declines of many migratory songbird populations across North America.

In the study, recently published in the influential Journal of Avian Biology, Western graduate student Yanju Ma and her collaborators in Western’s Department of Biology concluded that migratory songbirds with higher concentrations of mercury in their bodies were less likely to return from their migrations to southerly wintering locations.

Ma, who led the research with her joint supervisors Chris Guglielmo and Brian Branfireun and collaborator Keith Hobson, made the discovery after examining mercury concentrations and isotopes of hydrogen in tail feathers of migratory songbirds sampled at the Long Point Bird Observatory in southern Ontario.

The biologists compared mercury concentrations in the same species during the fall migration to the south and the returning population in the following spring and found that the songbirds with the highest mercury concentrations that also had to migrate long distances were not returning to their northern breeding grounds.

“Given all of the evidence that we have, we conclude that mercury is impairing the ability of some songbirds to successfully migrate,” says Ma. “Combined with our corresponding research, we are convinced that in some bird species, elevated mercury levels impact these birds’ neurology in a way that affects their ability to manage the challenging journey to their wintering grounds thousands of kilometres to the south.”

Western’s world-class research platforms were essential to this study as the Advanced Facility for Avian Research (AFAR), home to the world’s only hypobaric climatic wind tunnel for bird flight, its affiliated stable isotope facility and the Biotron Centre for Experimental Climate Change Research were utilized by Ma and her collaborators.

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