This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The eerie call of the common loon has long been the sound of North America's northern lakes, but new research shows it may not be that way in the future. A new study led by Birds Canada analyzed breeding attempts across nine Canadian provinces and seven U.S. states.
The researchers found a widespread, long-term plunge in loon chick production across their range. Published in the journal FACETS, the study evaluated 45,591 breeding events over 49 years. Scientists at Birds Canada led the analysis alongside university, government and conservation partners.
BRI's chief scientist and executive director, Dr. David Evers, and Lucas Savoy, BRI's deputy director, contributed their expertise to this study, which represents the largest and most comprehensive assessment of loon reproductive success ever conducted. In the past, loons had enough chicks to keep their overall population steady (roughly one surviving chick for every two breeding pairs).
However, chick production is now decreasing across 11 of the 12 regions studied. Some places have had steep drops in production, such as Atlantic Canada provinces and the prairie provinces, with 74% and 65% cumulative losses since 1992, respectively. Maine is the only region studied with a stable productivity trend of 0.17% per year.
Researchers point to a combination of human-caused disturbances and climate change factors as primary drivers behind the declining chick numbers. In particular, increased extreme rainfall events triggered by climate change disrupt loon breeding in three distinct ways: Beyond these range-wide trends, regional threats such as lead fishing tackle, methylmercury contamination, lake acidity, shoreline development and increased egg predation by bald eagles continue to depress reproductive output. Common loons are long-lived birds, with fairly high adult survival rates.
Thus, adult population counts on lakes can appear healthy even when reproductive success is failing. Researchers warn that sustained drops in chick production serve as a critical early warning sign of impending adult population declines across Ontario, other Canadian provinces, New York, Massachusetts and New Hampshire. "Identifying the root causes of productivity declines across different regions is essential to saving loon populations," the authors note.
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