A comprehensive new study has found significant declines in Common Loon populations across much of Canada, raising concerns about the future presence of this iconic species. Researchers from Canada and the United States combined decades of data in an effort published Thursday in the journal FACETS, revealing that loons are experiencing long-term downward trends in reproductive success in nearly all surveyed breeding regions.

Led by Matthew Fuirst, a research ecologist at Birds Canada, the study analyzed more than 45,000 breeding records collected from 3,421 lakes across North America. Data sources included contributions from volunteer participants in a longstanding Birds Canada survey, as well as other observational records dating back to the 1980s. The focus was on productivity—measured as the number of chicks per adult pair surviving six weeks post-hatching—to assess regional trends over periods spanning two to four decades.

The findings indicate “substantial long-term declines” in loon productivity in 11 of the 12 regions studied, with the steepest drops observed in Atlantic and Prairie provinces. Northern Maine was the only exception, where loon productivity has remained relatively stable. While loons are not currently classified as endangered, Canada hosts an estimated 254,000 breeding pairs, accounting for roughly 94 percent of the species’ total population, making these declines particularly noteworthy.

The patterns point to a complex interplay of factors affecting loons, including human disturbances to breeding habitats and possibly climate change. One speculative driver, highlighted by the researchers, involves increased precipitation linked to climate shifts. More frequent flooding and turbidity in lakes may reduce visibility, impairing loons’ fishing abilities. Unlike ducks, loons depend on clear waters to hunt fish, aided by dense bones that enable extended underwater dives. Any disruption to water clarity could, therefore, hamper their capacity to provide for their young.

Walter Piper, a co-author and biology professor at Chapman University, emphasized that declines may persist and worsen, noting additional evidence of decreased chick quality suggestive of poor nourishment. He cautioned that loons’ long lifespans could delay visible population impacts, underscoring the urgent need to identify causes now.

James Paruk, a biologist and loon expert at St. Joseph’s College in Maine who was not involved in the study, pointed to the relative lack of human development near northern Maine lakes as a possible factor in the more stable loon productivity there. He also commended the study for its extensive scope and methodological coordination, attributing its broad temporal and geographic scale as key to understanding these trends.

Dr. Fuirst indicated that ongoing research aims to pinpoint the specific threats driving loon declines, with the goal of mitigating impacts before they become irreversible. “If we can identify threats before they become detrimental, that’s the best-case scenario,” he said, highlighting the value of timely intervention for this species considered emblematic of Canadian wilderness and national identity.