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. Snow geese breed north of the timberline in Greenland, Canada, Alaska, and the northeastern tip of Siberia, and spend winters in warm parts of North America from southwestern British Columbia through parts of the United States to Mexico.
Taxonomy In 1750, English naturalist George Edwards included an illustration and a description of the snow goose in the third volume of his A Natural History of Uncommon Birds. He used the English name "the blue-winged goose". Edwards based his hand-coloured etching on a preserved specimen that had been brought to London from the Hudson Bay area of Canada by James Isham. 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
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 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 2.70 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).
Breeding Long-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 return to the place they hatched to breed. Snow geese often nest in colonies. Nesting usually begins at the end of May to 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. Eggs measure 7.9–8.3 cm (3.1–3.3 in) in length and 5.1–5.5 cm (2–2.2 in) in width. 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.
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.
… excerpt ends here. Continue reading the full article.
