The snow goose (Anser caerulescens), consisting of both a white morph and dark morph (blue goose), is a North American species of goose, collectively with Ross's goose often referred to as "white geese" or "light geese." Its name derives from the typically white plumage. Many taxonomic authorities placed this species and the other "white geese" in the genus Chen. Most authorities now follow the traditional treatment of placing these species in the "gray goose" genus Anser. The scientific name is from the Latin anser, "goose", and caerulescens, "bluish", derived from caeruleus, "dark blue".
This goose breeds north of the timberline in Greenland, Canada, Alaska, and the northeastern tip of Siberia, and spends winters in warm parts of North America from southwestern British Columbia through parts of the United States to Mexico. They fly as far south as Texas and Mexico during winter, and return to nest on the Arctic tundra each spring. It is a rare vagrant to Europe but for a frequent escape from collections and an occasional feral breeder. Snow geese are visitors to the British Isles where they are seen regularly among flocks of barnacle, Brent and Greenland white-fronted geese. There is also a feral population in Scotland from which many vagrant birds in Britain seem to derive.
In Central America, vagrants are frequently encountered during winter.
Description & appearanceThe snow goose has two color plumage morphs, white (snow) or gray/blue (blue), thus the common description as "snows" and "blues". White-morph birds are white except for black wing tips, but blue-morph geese have bluish-grey plumage replacing the white except on the head, neck and tail tip. The immature blue phase is drab or slate-gray with little to no white on the head, neck, or belly. Both snow and blue phases have rose-red feet and legs, and pink bills with black tomia ("cutting edges"), giving them a black "grin patch". The colors are not as bright on the feet, legs, and bill of immature birds. The head can be stained rusty-brown from minerals in the soil where they feed. They are very vocal and can often be heard from more than a mile away.
White- and blue-morph birds interbreed and the offspring may be of either morph. These two colors of geese were once thought to be separate species; since they interbreed and are found together throughout their ranges, they are now considered two color phases of the same species. The color phases are genetically controlled. The dark phase results from a single dominant gene and the white phase is homozygous recessive. When choosing a mate, young birds will most often select a mate that resembles their parents' coloring. If the birds were hatched into a mixed pair, they will mate with either color phase.
The species is divided into two subspecies on the basis of size and geography. Size overlap has caused some to question the division. The smaller subspecies, the lesser snow goose (C. c. caerulescens), lives from central northern Canada to the Bering Straits area. The lesser snow goose stands 64 to 79 cm (25 to 31 in) tall and weighs 2.05 to 2.7 kg (4.5 to 6.0 lb). The larger subspecies, the greater snow goose (C. c. atlanticus), nests in northeastern Canada. It averages about 3.2 kg (7.1 lb) and 79 cm (31 in), but can weigh up to 4.5 kg (9.9 lb). The wingspan for both subspecies ranges from 135 to 165 cm (53 to 65 in). Blue-morph birds are rare among the greater snow geese and among eastern populations of the lesser.
HabitatSnow geese breed from late May to mid-August, but they leave their nesting areas and spend more than half the year on their migration to-and-from warmer wintering areas. During spring migration (the reverse migration), large flocks of snow geese fly very high and migrate in large numbers along narrow corridors, more than 3,000 mi (4,800 km) from traditional wintering areas to the tundra.
The lesser snow goose travels through the Central Flyway, Mississippi Flyway, and Pacific Flyway across prairie and rich farmland to their wintering grounds on grassland and agricultural fields across the United States and Mexico, especially the Gulf coastal plain. The larger and less numerous greater snow goose travels through the Atlantic Flyway and winters on a relatively more restricted range on the Atlantic coastal plain. Traditionally, lesser snow geese wintered in coastal marsh areas where they used their short but strong bills to dig up the roots of marsh grasses for food. However, they have also since shifted inland towards agricultural areas, likely the cause behind the unsustainable population increase in the 20th century. This shift may help to contribute to increased goose survival rates, leading to overgrazing on tundra breeding grounds.
In March 2015, 2,000 snow geese were killed in northern Idaho from an avian cholera epidemic while flying their spring migration to northern Canada.
Hunting & foodOutside of the nesting season, they usually feed in flocks. In winter, snow geese feed on left-over grain in fields.
Breeding & matingLong-term pair bonds are usually formed in the second year, although breeding does not usually start until the third year. Females are strongly philopatric, meaning they will return to the place they hatched to breed.
Snow geese often nest in colonies. Nesting usually begins at the end of May or during the first few days of June, depending on snow conditions. The female selects a nest site and builds the nest on an area of high ground. The nest is a shallow depression lined with plant material and may be reused from year to year. After the female lays the first of three to five eggs, she lines the nest with down. The female incubates for 22 to 25 days, and the young leave the nest within a few hours of hatching.
Chicks, juveniles & raiseThe young feed themselves, but are protected by both parents. After 42 to 50 days they can fly, but they remain with their family until they are two to three years old.