Merlin

Ross's Goose Life History

Habitat

Habitat Lakes and Ponds

Ross’s Geese breed only in Canada, nesting in dry, low arctic tundra, usually near areas rich in sedges and grasses, often in patches of dwarf birch and willow on islands in small lakes. They sometimes nest among the “Lesser” subspecies of Snow Geese, although not when that species is nesting on stony areas. During fall migration, Ross’s stop at marshes and agricultural fields, where they eat barley, wheat, field peas, and wheatgrass. In spring, migrants feed in wet meadows and on native prairie plants on their northward migration. In winter, Ross’s use wetlands, grasslands, and agricultural fields during the day and roost overnight in wetlands, lakes, and reservoirs.

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Food

Food Plants

Ross’s Geese eat plant matter, rarely insects. When they arrive on breeding grounds, just as the tundra begins to thaw, they eat mostly roots of grasses and sedges. As the season progresses, they eat cottongrass, birch, and sedge shoots. Wintering birds eat cottongrass, chickweed, sedges, yellow sweet clover, common bulrush, spikerush, saltgrass, millet, barley, rice, corn, and other domestic grains. They forage while standing or walking slowly, grazing by picking short shoots, seeds, and grains. The larger-billed Snow Goose frequently digs outs roots and tubers, which Ross’s normally only does after heavy rains soften the ground.

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Nesting

Nest Placement

Nest Ground

Nests are built on tundra vegetation, either moss or heath, and seldom built on stony ground. Colonies are often on islands within lakes, rivers, or deltas.

Nest Description

Females build the nest from plant matter surrounding the nest (birch, willow, moss, grass, Labrador tea) and from down feathers from her brood patch. Nests average 18.4 inches across, with the interior cup 6.3 inches across and 3 inches deep. Compared to nests of the species’ nearest relative, Lesser Snow Goose, the nests of Ross’s are larger and more insulated.

Nesting Facts
Clutch Size:2-6 eggs
Number of Broods:1 brood
Egg Length:2.6-3.2 in (6.54-8.02 cm)
Egg Width:1.7-2.0 in (4.43-5.14 cm)
Incubation Period:19-25 days
Egg Description:

White, usually stained during incubation.

Condition at Hatching:

Covered with down and eyes open. Leaves nest within 24 hours of hatching and has the ability to swim and feed.

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Behavior

Behavior Ground Forager

Ross’s Geese form long-term monogamous pair bonds, although males sometimes attempt to mate with additional females. Courtship involves a male walking with short steps, rushing forward with his neck feathers pushed out. Then he pulls back, dips his head, and gives high-pitched, yelping calls. Pairs probably form in late winter or during spring migration, and copulation apparently occurs mostly during migration. Ross’s Geese nest in dense colonies (over 2,000 pairs per square mile) with Snow Geese of the subspecies caerulescens, called Lesser Snow Goose. Pairs select the nest site jointly and both defend the site, usually no more than 160 square feet. Ross’s Geese are generally peaceful, but they will threaten or attack other Ross’s or Snow Geese that intrude into the territory. They may walk toward intruders with bills raised and neck feathers fluttering, or they may race toward intruders with tail depressed, sometimes with bill open, making a hissing sound. On rare occasions, conflict escalates and the territorial male bites and holds the intruder with the bill while delivering sharp blows with the wings. Other threat postures involve bowing and head-dipping, which resemble courtship and pair-bonding displays. These are sometimes observed on the wintering grounds, where Ross’s come into frequent conflict with dominant Snow Geese. After an altercation on the breeding territory, male and female return to the nest site and perform a “triumph ceremony” that involves stretching out their necks, raising their bills, and giving a low, moaning call. Females incubate the eggs while males guard them, but females take occasional breaks to feed, and they cover the eggs with down at such times. Both parents attend and protect the goslings. After nesting, adults move to lowland areas where they molt their flight feathers, becoming flightless for a few weeks before migration. Unlike larger geese, Ross’s often do not maintain cohesive family units after migration.

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Conservation

Conservation Low Concern

In the mid-twentieth century, Ross’s Goose populations were low (in 1963 as few as 25,000 in California, their winter stronghold), but warming in the arctic has led to a steep increase in this species as well as in Snow Geese—to the point where the growing numbers of birds are overgrazing their tundra habitat. Partners in Flight estimates the global breeding population at 1.7 million. The group rates the species a 10 out of 20 on their Continental Concern Score, indicating it is a species of low conservation concern. Hunting, both on the nesting grounds and the wintering grounds, accounts for the largest known impact on Ross’s Goose populations. Hunting is carefully managed by the U.S. Fish and Wildlife Service; in recent years between about 50,000 and 100,000 Ross’s Geese have been shot by hunters each year. As a wetland species they are also sensitive to water pollution, and my be harmed by pesticides and other toxic materials.

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Credits

Jónsson, Jón E., John P. Ryder and Ray T. Alisauskas. (2013). Ross's Goose (Anser rossii), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

Raftovich, R. V., S. C. Chandler, and K. K. Fleming. (2018). Migratory bird hunting activity and harvest during the 2016-17 and 2017-18 hunting seasons. U.S. Fish and Wildlife Service, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, USA.

U.S. Fish and Wildlife Service. (2015). Waterfowl population status, 2015. Washington, DC: U.S. Department of the Interior.

Weckstein, J. D., A. D. Afton, R. M. Zink and R. T. Alisauskas. (2002). Hybridization and population subdivision within and between Ross's Geese and Lesser Snow Geese: A molecular perspective. Condor 104 (2):432-436.

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