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Common Merganser - Mergus merganser
Large diving duck. Males are 60 to 71 cm, 1700 g; females 54 to 68 cm, 1230 g. Male has greenish-black head, white neck and underparts, black upper wings, gray back and tail, and long narrow scarlet-orange bill. Female has rusty-brown head with long crest and white chin patch, gray breast, back, wings and tail with white flanks and belly and scarlet-orange bill (Mallory and Metz 1999).
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
SUMMER (Feb 16 - Dec 14)
Direct Evidence of Breeding
Indirect Evidence of Breeding
No Evidence of Breeding
WINTER (Dec 15 - Feb 15)
Not Regularly Observed
(Observations spanning multiple months or years are excluded from time charts)
During summer in the Bozeman area, Common Mergansers occur on large lakes and large rivers. During migration, most birds are on lakes (in the largest concentrations) (Skaar 1969).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: mtnhp.org/requests
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
The Common Merganser eats primarily small fish, but will also eat insects, mollusks, crustaceans, worms, frogs, small mammals, birds, and plants (Mallory and Metz 1999).
Pair formation appears to occur during late winter-early spring. Females breed in their second year, generally laying one clutch of 10 eggs with an incubation period of 32 days. Near Fortine, young about 1/3 grown were seen on June 14. Bozeman area migration periods are March 15 to May 5 and September 20 to December 15, with peaks April 5 and November 15. Young have been seen as early as May 31 (Skaar 1969). Nesting records statewide are from late March to late May.
- Literature Cited AboveLegend: View Online Publication
- Mallory, M. L., and K. Metz. 1999. Common Merganser (Mergus merganser). In The birds of North America, No. 442 (A. Poole and F. Gill, Eds.). Academy of Natural Sciences of Philadelphia and American Ornithologists’ Union. [Revised online 15 June 2015]
- Marks, J.S., P. Hendricks, and D. Casey. 2016. Birds of Montana. Arrington, VA. Buteo Books. 659 pages.
- Skaar, P.D. 1969. Birds of the Bozeman latilong: a compilation of data concerning the birds which occur between 45 and 46 N. latitude and 111 and 112 W. longitude, with current lists for Idaho, Montana, Wyoming, impinging Montana counties and Yellowstone National Park. Bozeman, MT. 132 p.
- Additional ReferencesLegend: View Online Publication
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- Johnson, D.D. 1991. Results of stream surveys for Harlequin ducks in the Gallatin and a section of the Custer National Forests, Montana. Unpublished report to the Montana Natural Heritage Program. 18 pp.
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- Joslin, Gayle. 1980. Wildlife inventory and hard rock mining impact analysis of the West Cabinet Mountains and Lake Creek Valley, Lincoln County, Montana. MTFWP 91 pgs + 47 pgs app.
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- MT Fish, Wildlife & Parks. No date. Blackfoot-Clearwater Wildlife Management Area checklist.
- Northrop, Devine and Tarbell, Inc. 1995. Cabinet Gorge and Noxon Rapids Hydroelectric Developments, 1994 Wetland Mapping and Assessment Study, Volume I of II. 27 pp. plus appendices.
- Oechsli, L.M. 2000. Ex-urban development in the Rocky Mountain West: consequences for native vegetation, wildlife diversity, and land-use planning in Big Sky, Montana. M.Sc. Thesis. Montana State University, Bozeman. 73 p.
- Palmer, R.S. 1962. Handbook of North American birds. Volume 1. Loons through flamingos. Yale University Press, New Haven. 567 pp.
- Reinhart, D.P. 1990. Grizzly bear habitat use on cutthroat trout spawning streams in tributaries of Yellowstone Lake. M.Sc. Thesis. Bozeman, MT: Montana State University. 128 p.
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- Rundquist, V.M. 1973. Avian ecology on stock ponds in two vegetational types in north-central Montana. Ph.D. Dissertation. Bozeman, MT: Montana State University. 112 p.
- Sater, S. 2022. The insects of Sevenmile Creek, a pictorial guide to their diversity and ecology. Undergraduate Thesis. Helena, MT: Carroll College. 242 p.
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- Sibley, D. 2014. The Sibley guide to birds. Alfred A. Knopf, New York, NY. 598 pp.
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- Waldt, R. 1995. The Pine Butte Swamp Preserve bird list. Choteau, MT: The Nature Conservancy. Updated August 1995.
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- Western Energy Co., Colstrip, MT., 1982, Western Energy Company Rosebud Mine, Colstrip, Montana: Annual Wildlife Report, 1982.
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