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Montana Field Guide

Montana Field Guides

Ross's Goose - Anser rossii

Native Species

Global Rank: G4
State Rank: S4N

Agency Status


External Links

General Description
Ross's Goose is the smallest of three varieties of white (snow) geese that breed in North America. White with black primaries. Mean length: male 621.3 mm, female 587.6 mm. Mass: male 1484 g, female 1340 g. Species is monochromatic and sexually dimorphic. Plumage is similar to white morph of Greater and Lesser Snow geese. The relatively short neck of Ross's Goose gives it an abbreviated silhouette. Feather of lore meet base of maxilla forming a straight line instead of a forward curved arc typical of Greater and Lesser Snow Geese. Head, usually lacking an orange ferrous stain frequently found on Greater and Lesser Snow Geese, is diminutive and rounded (Ryder and Alisauskas 1995).

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.

Species Range
Montana Range Range Descriptions


Western Hemisphere Range


Observations in Montana Natural Heritage Program Database
Number of Observations: 739

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density


SUMMER (Feb 16 - Dec 14)
Direct Evidence of Breeding

Indirect Evidence of Breeding

No Evidence of Breeding

WINTER (Dec 15 - Feb 15)
Regularly Observed

Not Regularly Observed


(Observations spanning multiple months or years are excluded from time charts)

Most migration occurs through northwest and west-central Montana. Single or small groups of Ross's geese often migrate with Snow Geese. About 20,000 to 40,000 stop at Freezeout Lake Wildlife Management Area each spring and fall; this is approximately 20% of the total world population (Schwitters, personal communication).

Low arctic tundra. Currently about 95% of all Ross's Geese nest in the Queen Maud Gulf Migratory Bird Sanctuary in central Canadian Arctic. Landscape is dominated by flat plain or postglacial marine emergence. The main wintering area for the species is presently in the Central Valley of California. It seldom associates with the largest snow goose, Greater Snow Goose; but is often found in the company of the intermediate-sized Lesser Snow Goose. During spring and fall migration feeds and roosts in marshes. In northeast California, uses grain fields and wet meadows for foraging (Ryder and Alisauskas 1995).

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:
    1. 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);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
    4. 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: 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.

    Literature Cited
    • 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.

Food Habits
Strictly vegetarian. Foods taken include grasses, sedges, legumes, and domestic grains (Ryder and Alisauskas 1995).

Reproductive Characteristics
Nests on the ground, preferably in areas with a variety of low vegetation or rock/gravel that provide protections from wind. Eggs are near subelliptical, nonglossy white or light cream colored. Clutch size is 2 to 6 eggs, usually 4. At Arlone and Karrak lakes, laying occurs in first 3 weeks in June, with peak normally in first to second week. Hatching occurs from late June to mid-July, with peak in first to second week in July (Ryder and Alisauskas 1995).

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Ross's Goose — Anser rossii.  Montana Field Guide.  .  Retrieved on , from