Declining population of Harlequin Duck (Histrionicus histrionicus) on the Bow River, Alberta, Canada: 25 years of monitoring

A 25-year study on the Harlequin Duck population along the Bow River in Banff National Park, Alberta, reveals a concerning 3.3% annual decline from 1995 to 2020, despite the site's protected status. The research, using roadside surveys and state-space modeling, identified distinct phases: stability until 2005, followed by steep decline until 2011, and recent stabilization with slight rebound. Notably, the male-to-female ratio dropped during population decline, suggesting potential breeding challenges. This trend mirrors declines in other Rocky Mountain regions and coastal wintering areas, indicating broader ecological stressors rather than localized issues.

Smith, C., Shepherd, B., Bradley, M., & Humphries, S. (2024). Declining population of Harlequin Duck (Histrionicus histrionicus) on the Bow River, Alberta, Canada: 25 years of monitoring. The Canadian Field-Naturalist, 137(4), 358–366. https://doi.org/10.22621/cfn.v137i4.3183