Common Merganser
(Mergus merganser)


Picture of bird
© Jukka Jantunen (
For additional photos and vocalizations, visit Dendroica. (Link opens in a new window.)

The Common Merganser is the largest of the three North American merganser species. It breeds across Canada in areas where trees are large enough to support suitable nesting cavities. The population size and trend for mergansers are not reliably known, as many aerial surveys do not distinguish between Common and Red-breasted Mergansers, whose breeding range overlap extensively. An important part of the species’ breeding range, the Boreal forest, is not covered very well by current surveys. However, the three merganser species can be reliably identified during helicopter-based plot surveys. In eastern Canada, Common Merganser numbers appear to have remained stable since the survey first began in the 1990s. Overall, this species is not heavily harvested by hunters. The harvest of Common Mergansers has been decreasing since the 1980s, with most of the harvest occurring in eastern Canada. This species has been identified as a priority for conservation and/or stewardship in one or more Bird Conservation Region Strategies in Canada.


Main designations for the species
DesignationStatusDateSubspecies, population
IUCN (Global)Least concern2018 
Wild Species (Canada)Secure2015 
Bird Conservation Region StrategyPriority Species2013 

Population status

Geographic area or populationPopulation change relative to ~1970ReliabilityStatus in relation to goal
CanadaLittle ChangeMediumAt an Acceptable Level

Population estimate

Geographic area or populationPopulation estimate
Canada1,000,000 - 5,000,000 birds

Distribution maps


Migration strategy, occurrence

Short-distance migrant

Responsibility for conservation

Geographic areaResponsibility based on % of global population

General nesting period in Canada

Nesting period starts between late March and late May and ends between mid-July and early August, depending on the region. Before or after this period, the probability of an active nest is lower.

Conservation and management

The most important factor limiting the population size and breeding distribution of the Common Merganser is probably the availability of fish, but suitable nesting cavities can also play a role locally. In areas that were or are being logged, forestry practices may have reduced the availability of cavities suitable for nesting. Lake acidification and associated declines in fish populations can also reduce habitat quality (Pearce et al. 2015). Due to their trophic level, Common Mergansers are vulnerable to contaminants (e.g., mercury, lead), and may be useful bioindicator species for fish-bearing streams and lakes (Pearce et al. 2015).


Bird conservation region strategies

Environment and Climate Change Canada and partners have developed Bird Conservation Region Strategies in each of Canada’s Bird Conservation Regions (BCRs). In these strategies, selected species are identified as priorities for one or more of the following reasons:

  • conservation concerns (i.e., species vulnerable due to population size, distribution, population trend, abundance, or threats)
  • stewardship responsibilities (i.e., species that typify the regional avifauna or have a large proportion of their range or population in the sub-region)
  • management concerns (i.e., species that require ongoing management because of their socio-economic importance as game species, or because of their impacts on other species or habitats)
  • other concerns (i.e., species deemed a priority by regional experts for other reasons than those listed above or because they are listed as species at risk or concern at the provincial level)

Select any of the sub-regions below to view the BCR strategy for additional details.

BCRs, marine biogeographic units, and sub-regions in which the species is listed as a priority
RegionSub-region and priority type
Boreal Hardwood TransitionBoreal Hardwood Transition, sub-region and priority type: Ontario and Manitoba -- Conservation
Boreal Softwood ShieldBoreal Softwood Shield, sub-region and priority type: Atlantic, NL -- Other
Boreal Softwood ShieldBoreal Softwood Shield, sub-region and priority type: Ontario -- Conservation
Lower Great Lakes/St. Lawrence PlainLower Great Lakes/St. Lawrence Plain, sub-region and priority type: Ontario -- Conservation
Newfoundland and Labrador Shelves Newfoundland and Labrador Shelves , sub-region and priority type: Atlantic, NL -- Other
Taiga Shield and Hudson PlainsTaiga Shield and Hudson Plains, sub-region and priority type: Ontario -- Conservation