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Characteristics and Range The Common Merganser, a large, fish-eating duck with a long, pointed and serrated bill, is a familiar sight on rivers, lakes and near-shore coastal waters. This widespread and largest species of merganser breeds throughout temperate forested habitats of the Northern Hemisphere (Johnsgard 2010). In North America, it breeds in boreal forest, montane forest and aspen parkland from treeline south to the Great Lakes (Pearce et al. 2015). A short-distance migrant, it winters on both fresh and salt water from its southern breeding range to northern Mexico and the mid-Atlantic coast.

Distribution, Abundance, and Habitat The Common Merganser is a widespread year-round resident in British Columbia wherever lakes or rivers don't freeze over in winter, particularly in coastal regions and the central-southern interior; it is only absent in extremely mountainous areas (Campbell et al. 1990). It occupies a wide elevation range, but most nesting is below about 750 m.

The most extensive areas of highest Probability of Observation are in the Coast and Mountains and Georgia Depression ecoprovinces, including Haida Gwaii. Atlas point count data indicate these ecoprovinces and the Southern Interior and Southern Interior Mountains ecoprovinces support the core of the provincial population, with highest abundance occurring below about 500 m elevation. Size and trends of populations in North America are not reliably known (aerial surveys of breeding birds often do not differentiate between Common and Red-breasted mergansers, and large portions of their range are not surveyed).

Large lakes and rivers bordered by conifers or mixed forests mature enough to provide suitable tree cavities are preferred nesting habitat; most records and highest abundances on Atlas point counts were in conifer-dominated biogeoclimatic zones. The Common Merganser nests in any suitable cavity in live or dead trees, as well as crevices in rock or silt cliffs.

Conservation and Recommendations Perhaps the most important factor limiting Common Merganser populations is the availability of nest cavities; logging can have a detrimental effect by removing larger trees suitable for nesting. Elevated levels of industrial contaminants have been recorded in the Common Merganser in coastal British Columbia (Elliott and Martin 1989) and can affect their health (Pearce et al. 2015).

Art Martell

Recommended citation: Martell, A. 2015. Common Merganser in Davidson, P.J.A., R.J. Cannings, A.R. Couturier, D. Lepage, and C.M. Di Corrado (eds.). The Atlas of the Breeding Birds of British Columbia, 2008-2012. Bird Studies Canada. Delta, B.C. http://www.birdatlas.bc.ca/accounts/speciesaccount.jsp?sp=COME&lang=en [09 Oct 2024]