Ross's Goose

Ross's Geese nest in dense colonies on the Arctic tundra, typically alongside Lesser Snow Geese. Colony densities can exceed 2,000 pairs per square mile, with recorded nest densities of 3–64 nests per 1,000 m². Nest sites are usually on islands or shores of tundra lakes, often at the edge of low thickets, on moss, short grass, or gravel. The same site is frequently reused in successive seasons.

The female builds the nest from plant material immediately surrounding the site — birch, willow, moss, grass, and Labrador tea — and lines it with down feathers from her brood patch, beginning around the time the first egg is laid. Nests average 47 cm across, with an interior cup 16 cm across and 7.6 cm deep, making them larger and better insulated than the nests of the closely related Lesser Snow Goose.

Clutch size is typically 4 eggs (range 2–6, rarely 1–8), dull white and becoming nest-stained during incubation. Eggs average 6.5–8.0 cm long and 4.4–5.1 cm wide, weighing approximately 94 g. The female incubates alone for 19–25 days (typically 21–23 days), while the male stands guard and defends the territory, occasionally covering the eggs during the female's brief foraging breaks.

Goslings hatch covered in down with eyes open and leave the nest within 24 hours. They can swim and feed themselves almost immediately. Both parents attend and protect the young. Fledging occurs at 40–45 days. After nesting, adults move to lowland areas to moult their flight feathers, becoming temporarily flightless before migration begins. Nest success is closely tied to snowmelt timing — later snowmelt leads to fewer nesting attempts and smaller clutch sizes. First breeding typically occurs at age 2–3 years.

Ross's Geese typically live between 6 and 15 years in the wild, with the maximum recorded lifespan standing at 22 years and 6 months — a female banded in Saskatchewan in 1972 and recovered in California in 1993. This figure almost certainly underestimates the true potential lifespan: five of the six oldest recorded individuals were taken by hunters rather than found dead naturally, meaning birds that avoided hunting pressure may have lived longer still.

Survival rates are influenced by several factors. Predation on the breeding grounds — primarily by Arctic foxes, large gulls, and raptors targeting eggs and goslings — is the main source of mortality for young birds. Adults face fewer natural predators, and hunting is now the primary cause of mortality for birds that survive to adulthood. An average of 63,825 birds were harvested per season in the US during 2019–2022, with California, Texas, and Arkansas accounting for the largest harvests.

Compared to larger geese, the Ross's Goose has a relatively short typical lifespan, reflecting its smaller body size — larger-bodied geese such as the Canada Goose regularly exceed 20 years in the wild. However, the species' rapid population growth (11.7% per year between 1975 and 2014) suggests that overall survival rates are high and that annual productivity consistently exceeds mortality across the population. Climate change poses an emerging threat to survival rates, particularly through its effects on Arctic snowmelt timing, which directly influences nest success and gosling survival in the critical early weeks of life.

Ross's Goose is listed as Least Concern by the IUCN (2016), and its population trajectory is one of the most dramatic recoveries in North American ornithology. The primary historical threat was market hunting: extensive shooting and trapping drove the entire world population to just 2,000–3,000 birds in the early 1950s, with as few as 25,000 birds recorded in California in 1963. Hunting was made illegal in the US in 1931 under the Migratory Bird Treaty Act, and the population responded spectacularly.

By 1988, 188,000 breeding birds were recorded. By 2006, the population had reached 1.3 million. The most recent estimate stands at approximately 2.35 million birds, with Partners in Flight estimating the global breeding population at 1.7 million. Growth has averaged 11.7% per year between 1975 and 2014 — an overall increase of approximately 8,900% in roughly 40 years. The species scores just 10 out of 20 on the Partners in Flight Continental Concern Score, indicating low conservation concern. Restricted hunting was reintroduced as populations recovered, with an average of 63,825 birds harvested per season in the US during 2019–2022.

Paradoxically, the population explosion has itself become an ecological problem. Growing colonies of Ross's and Snow Geese are overgrazing vast areas of Arctic tundra, stripping vegetation nearly to bare ground — damage now visible from space. Wildlife agencies are actively exploring population management measures to protect the broader tundra ecosystem. Other current threats include loss of migration stopover and wintering wetland habitats, climate change altering Arctic snowmelt timing and vegetation green-up, low genetic diversity from the historic population bottleneck, and potential harm from pesticides and water pollution in agricultural wintering areas.

The Ross's Goose has one of the more convoluted naming histories of any North American bird. The species was first described in Western literature by explorer Samuel Hearne in 1770, who encountered it during his overland journey to the Arctic Ocean and called it the "horned wavey" — a reference to the warty caruncles at the base of the bill ("horned") and the Cree word for goose ("wavey" or "wavy"). Despite this early description, the bird was not formally named by science until 1861, when American ornithologist John Cassin described it as Chen rossii, naming it in honour of Bernard Rogan Ross, a Hudson's Bay Company trader and naturalist who collected specimens from the Northwest Territories.

Most remarkably, the species' Arctic breeding grounds were not discovered by Western science until 1938 — making it one of the last North American bird species to have its nesting colonies located, nearly 170 years after Hearne's first written description. The discovery was made by Dewey Soper, a Canadian naturalist, at the Queen Maud Gulf in what is now Nunavut.

The species has been placed in two genera over its taxonomic history. It was long classified as Chen rossii (in the genus Chen, alongside the Snow Goose and Emperor Goose), but is now placed in Anser by most authorities, including the International Ornithological Congress, reflecting molecular evidence that the white geese are not a distinct lineage from the grey geese. The common name honours Bernard Ross, though the possessive apostrophe placement (Ross's rather than Ross') follows standard ornithological convention for eponymous species names.

Ross's Geese form long-term monogamous pair bonds, likely maintained for life as in other goose species. Pairs probably form in late winter or during spring migration, with courtship behaviour observed from February onward. The male initiates courtship by walking toward the female with short, deliberate steps, neck feathers pushed out to increase apparent size. He then pulls back, dips his head repeatedly, and gives a series of high-pitched, yelping calls — a display that is more energetic and insistent than the subtle head movements of larger goose species.

Copulation apparently occurs mostly during migration rather than on the breeding grounds. Males occasionally attempt to mate with additional females, but these attempts typically fail due to the female's active resistance and the intervention of her mate.

One of the most distinctive social behaviours is the "triumph ceremony" performed after territorial disputes. Once a rival has been driven off, both members of the pair stretch their necks forward and upward, raise their bills skyward, and give a low, moaning call in unison — a coordinated display that reinforces the pair bond and signals joint ownership of the territory to neighbouring birds. This ceremony is common to many goose species but is particularly well-documented in Ross's Goose due to the species' colonial nesting habits, where territorial interactions are frequent.

Non-vocal communication also plays a role in social interactions: birds vibrate their raised neck feathers as a postural signal during territorial encounters, conveying threat or submission without vocalisation. On the breeding grounds, the male stands guard near the incubating female, defending the nest against neighbouring pairs and potential predators, and the pair's bond is reinforced through repeated triumph ceremonies throughout the breeding season.