Over the past two decades, BRI has conducted extensive non-lethal sampling of Common Loons (Gavia immer) throughout North America to assess continental mercury (Hg) trends among lakes and ponds, and using the loon as a keystone aquatic indicator species. In 1997 and 1999, BRI and Canadian collaborators conducted loon Hg investigations on 31-Mile Lake and Pemichangan Lake, a complex of large lakes located in southwestern Quebec.
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Mercury in Loons
During 1997-1999, BRI biologists captured, banded, and collected blood and feather samples from 19 loons among 31-Mile and Pemichangan Lakes, to screen for their Hg concentrations. Overall, loons from both lakes contained Hg concentrations considered to be of low risk to accumulation by loons. Pemichangan Lake contained slightly higher levels of Hg in loons than those from 31-Mile Lake.
In addition to sampling for Hg, each captured adult loon is weighed (to determine gender), measured, and uniquely marked using combinations of plastic color leg bands, accompanied with a federal metal leg band. The banding of loons provides a reliable field method to re-observe individuals over many years and to track whether or not they are returning to their breeding lakes each summer. Additionally, banded loons are occasionally encountered alive or deceased on their non-breeding areas. A recovered banded loon provides important information on that individual’s or possibly, an entire breeding population’s wintering range.
Of the 19 loons previously banded on this project’s lakes in Quebec, two loons, each from 31-Mile Lake, have been recovered. A male banded in 1999, was found dead on December 31, 2001 at Ormond Beach, located on the Atlantic coast of Florida. The other loon was accidentally caught and drowned in a fishing net on October 2, 2013 on 31-Mile Lake. This loon was a male banded in 1997 and was recovered 13 years later, which means this loon would have been at least 17 years old when it died.
A 20-Year Follow-Up
BRI and members from the Gatineau Fish & Game Club in Quebec are partnering to conduct loon studies on 31-Mile and Pemichangan Lakes in 2019. The re-sampling of loons breeding on those lakes will provide a valuable reassessment of Hg concentrations from the same lakes 20-22 years later. Data collected during this study would enhance our knowledge in assessing long-term Hg trends among lakes and ponds and the wildlife that inhabit them in eastern North America.
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