Common Loons Threatened by Declining Water Clarity

by Carly Murphy, Chapman University
April 05, 2024

The Common Loon, an icon of the northern wilderness, is under threat from climate change due to reduced water clarity, according to a new study authored by Chapman University professor, Walter Piper. The study, published April 1 in Ecology, followed up an earlier paper that showed substantial reproductive decline in the author’s study area in northern Wisconsin.

The paper is the first clear evidence demonstrating an effect of climate change on this charismatic species. Specifically, the paper shows that July rainfall results in reduced July water clarity in loon territories. Reduced water clarity, in turn, makes it difficult for adult loons to find and capture their prey (mainly small fishes) under water, so they are not able to meet their chicks’ metabolic needs. The result is low chick weight and higher chick mortality. Since loons use the same foraging mode across their breeding range, the impact of water clarity on loon breeding success found in Wisconsin is likely to be echoed from Alaska to Iceland.

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