Montana Field Guide

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.

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).

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

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).