thumb|A pair of snow geese calling

The snow goose (Anser caerulescens) is a species of goose native to North America. Both white and dark morphs exist, the latter often known as blue goose. Its name derives from the typically white plumage. The species was previously placed in the genus Chen, but is now typically included in the "gray goose" genus Anser. When in 1758 the Swedish naturalist Carl Linnaeus updated his Systema Naturae for the 10th edition, he placed the snow goose with the ducks and geese in the genus Anas. Linnaeus included a brief description, coined the binomial name Anas caerulescens, and cited Edwards' work. The snow goose is now placed in the genus Anser that was introduced by French zoologist Mathurin Jacques Brisson in 1760. The scientific name is from the Latin anser, "goose", and caerulescens, "bluish", derived from caeruleus, "dark blue". The snow goose is the sister species to Ross's goose (Anser rossii).

Two subspecies are recognised:

  • A. c. atlanticus (Kennard, 1927) – greater snow goose – breeds in northeast Canada and northwest Greenland, winters in northeast USA
  • A. c. caerulescens (Linnaeus, 1758) – lesser snow goose – breeds in northeast Siberia, north Alaska, and northwest Canada, winters in south USA, north Mexico and Japan

The greater snow goose is distinguished from the nominate form by being slightly larger. It nests farther north and east. The lesser snow goose can be found in two color phases, the normal white-colored animals and a dark gray-colored "blue" phase. The greater snow goose is rarely seen in a blue phase.

Description

thumb|Snow goose at the Gray Lodge Wildlife Area in Northern California

The 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-gray 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". These colors distinguish the species from white domesticated geese. 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 most often select a mate that resembles their parents' coloring. If the birds were hatched into a mixed pair, they 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 female incubates for 22 to 25 days, and the young leave the nest within a few hours of hatching.

The 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.

thumb|[[Ross's goose (foreground) and snow goose (background), in Louisiana]]

Where snow geese and Ross's geese breed together, as at La Pérouse, they hybridize at times, and hybrids are fertile. Rare hybrids with the greater white-fronted goose, Canada goose, and cackling goose have been observed.

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.

Vagrancy

The snow goose is a rare vagrant to Europe, but escapes from collections have occurred, and it is an occasional feral breeder. Snow geese are visitors to the British Isles, where they are seen regularly among flocks of brant, barnacle goose, and greater white-fronted goose. Also, a feral population occurs in Scotland from which many vagrant birds in Britain seem to derive.

Around 2015, a small group of three to five snow geese landed on the north shore of O'ahu. They were seen and photographed several times over the course of 3–4 months.

In Central America, vagrants are frequently encountered during winter.

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File:Anser caerulescens MHNT.ZOO.2010.11.15.1.jpg|Anser caerulescens - MHNT

File:Greater Snow Geese.jpg|A. c. atlanticus, spring migration, blue morphs in foreground, Alexandria, Ontario

File:Chen caerulescens 32880.JPG|Wintering snow geese on Fir Island, Washington

File:Landing Snow Goose.jpg|Snow goose landing

File:Snow Geese in Fir Island field - 2009.jpg|Snow geese in a corn field on Fir Island, Washington in the Skagit River delta

File:Greater Snow Geese.ogg|Greater snow geese in flight

File:Anser caerulescens CT8.jpg|Snow geese (Anser caerulescens)

File:Chemin_de_l%27Ile_du_Large_006.jpg|Snow geese on the North shore of the St. Lawrence River at Sainte-Anne-de-la-Pérade, Quebec, Canada

</gallery>

References

Further reading

  • Conservation Order for Light Geese - Cornell Law School
  • Snow Goose Species Account – Cornell Lab of Ornithology
  • The Nature Conservancy's Species profile: Snow Goose Learn more about the conservation of these geese
  • Snow Goose - Chen caerulescens – USGS Patuxent Bird Identification InfoCenter
  • Song of the North Wind: A Story of the Snow Goose by Paul A. Johnsgard (1974, rev. 2009)