There are two distinct populations of Harlequin Duck in North America: the Western population, breeding largely in the Rocky Mountains and wintering along the Pacific coast, and a much smaller Eastern population, breeding in northern Quebec and Newfoundland and Labrador, and wintering primarily off Greenland and along the Atlantic coast of Canada and the northeastern United States. 

The Western population is estimated to have at least 150,000 individuals, while the most recent population estimate for the Eastern population is 5,700 (Gutowsky et al., 2022). The Eastern population was assessed as Endangered by the Committee on the Status of Endangered Wildlife in Canada in 1990, but reassessed as Special Concern in 2001 and 2013, and is listed at that level under the Species at Risk Act as Special Concern. However, Christmas Bird Count (CBC) data indicate a large increase in the Eastern population since 1970, and it is within its goal range. The Western population is also best monitored by regional CBC trends, which show little long-term change. The national population is dominated by the much larger western population, and also shows little change relative to 1970. Confidence in all status assessments is medium because of limitations in CBC coverage, and lack of standardized data collection.