Population status

Common Merganser
(Mergus merganser)

The population size and trends for mergansers are not reliably known, as many aerial surveys do not distinguish among the three species, whose breeding ranges overlap extensively. In addition, the boreal forest, which is an important part of the merganser breeding range, is not covered very well by many surveys. However, the three species can be reliably identified during helicopter-based plot surveys conducted as part of the Eastern Waterfowl Breeding Ground Survey. The Common Merganser is also monitored by the Southern Ontario Waterfowl Plot Survey. Trends in eastern Canada show an overall increase in population. The continental Common Merganser population size is estimated at 1.2 million birds (North American Waterfowl Management Plan 2012). This species is at an acceptable level relative to its national population goal. Detailed information on the population status of waterfowl species is available in the Population Status of Migratory Game Birds in Canada report (summarized version). To obtain a copy of the full version of this report, including tables and graphs, please contact ec.scf-oismiggibiers-cws-miggamebirds.ec@canada.ca.

Population goal and acceptable levels of variation

Species/group	Goal	Lower level	Upper level
Canada	Long-term average of the time series	10th percentile of observed abundance (1970-2012)	Not applicable

British Columbia Coastal Waterbird Survey

Additional information on: British Columbia Coastal Waterbird Survey

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Table 1: Population trends by geographic area
Geographic area	Time Period	Annual Trend ^{Table 1 - footnote 1}	Limits
Geographic area	Time Period	Annual Trend ^{Table 1 - footnote 1}	Lower	Upper
British Columbia coast	1999-2016	0.8	-1.5	3.4

Eastern waterfowl breeding ground survey

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Table 2: Population trends by geographic area
Geographic area	Time Period	Annual Trend ^{Table 2 - footnote 1}	Limits
Geographic area	Time Period	Annual Trend ^{Table 2 - footnote 1}	Lower	Upper
Total survey area Select to view graph of the geographic area: Total survey area 1990-2017; Eastern waterfowl breeding ground survey	1990-2017	0.9	-0.5	2.3

Southern Ontario Waterfowl Plot Survey

Additional information on: Southern Ontario Waterfowl Plot Survey

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Table 3: Population trends by geographic area
Geographic area	Time Period	Annual trend ^{Table 3 - footnote 1} ^{Table 3 - footnote 2}	Limits
Geographic area	Time Period		Lower	Upper
Southern Ontario Select to view graph of the geographic area: Southern Ontario 1971-2017; Southern Ontario Waterfowl Plot Survey	1971-2017	7.9	3.1	14.5

References

Canadian Wildlife Service (CWS) Waterfowl Committee. 2017. Population Status of Migratory Game Birds in Canada: November 2017. CWS Migratory Birds Regulatory Report Number 49. 221 pp. Canadian Wildlife Service (CWS) Waterfowl Committee. 2017. Population Status of Migratory Game Birds in Canada: November 2017. CWS Migratory Birds Regulatory Report Number 49. 221 pp. (Link)
North American Waterfowl Management Plan. 2012. North American Waterfowl Management Plan 2012: People Conserving Waterfowl and Wetlands. Canadian Wildlife Service, U.S. Fish and Wildlife Service, and Secretaria de Medio Ambiente y Recursos Naturales. xii + 48 pp. North American Waterfowl Management Plan. 2012. North American Waterfowl Management Plan 2012: People Conserving Waterfowl and Wetlands. Canadian Wildlife Service, U.S. Fish and Wildlife Service, and Secretaria de Medio Ambiente y Recursos Naturales. xii + 48 pp. (Link)
Pearce, J., M. Mallory and K. Metz. 2015. Common Merganser (Mergus merganser), The Birds of North America Online (A. Poole, Ed.). Cornell Lab of Ornithology, Ithaca, New York. Pearce, J., M. Mallory and K. Metz. 2015. Common Merganser (Mergus merganser), The Birds of North America Online (A. Poole, Ed.). Cornell Lab of Ornithology, Ithaca, New York. (Link)