Snow Goose

Snow geese are known for their white plumage, but many of them are actually darker, gray-brown birds known as blue geese. These birds were once though to be two separate species, but they have recently been found to be merely two different color morphs of the same bird. A single gene controls the color difference.

Snow geese are harbingers of the changing seasons. They fly south for the winter in huge, honking flocks that may appear as a “U” formation or simply as a large “snowstorm” of white birds. They spend the colder seasons in southern coastal marshes, bays, wet grasslands, and fields. Their diet is entirely vegetarian, consisting of grasses and grains, grazed from damp soils or even shallow water.

At winter’s end, snow geese fly north to their breeding grounds on the Arctic tundra. Pairs mate for life, and produce two to six eggs each year in a shallow ground nest. Chicks can swim and eat on their own within 24 hours, but families remain together through the young’s first winter. Families can be identified as groups during both the southern and northern migrations.

In 1916, snow geese had become so rare in the eastern United States that hunting of the species was banned. Since that time, the birds have made a remarkable comeback. Today, though hunting has been reinstated, populations are thriving. In fact, the birds have become so numerous in places that they threaten to destroy their own habitat.

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-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 25 to 31 inches (63 to 79 cm) tall and weighs 4.5 to 6.0 pounds (2.0 to 2.7 kg). 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.

Breeding

Long-term pair bonds (they mate for life) 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 3 to 5 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.

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 2 to 3 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.

Population

The breeding population of the Lesser Snow Goose exceeds 5 million birds, an increase of more than 300 percent since the mid-1970s. The population is increasing at a rate of more than 5 percent per year. Non-breeding geese (juveniles or adults that fail to nest successfully) are not included in this estimate, so the total number of geese is even higher. Lesser Snow Goose population indices are the highest they have been since population records have been kept, and evidence suggests that large breeding populations are spreading to previously untouched sections of the Hudson Bay coastline.

Cool Facts

• Snow Goose hunting in the eastern United States was stopped in 1916 because of low population levels. Hunting was allowed again in 1975 after populations had increased. Populations have been growing so large that the geese are destroying nesting habitat. Hunting has not slowed the dramatic increases in population size.
• One nest was found to be attended by two female Snow Geese, but no male. Each female had been inseminated by a different male and both incubated the eggs.
• The dark color of the blue morph Snow Goose is controlled by a single gene, with dark being partially dominant over white. If a pure dark goose mates with a white goose, the offspring will all be dark (possibly with white bellies). If two white geese mate, they have only white offspring. If two dark geese mate, they will have mostly dark offspring, but might have a few white ones too.
• Parents stay with their young through the first winter. Families travel together on both the southbound and northbound migrations, separating only after they return to the arctic breeding grounds. Family groups can easily be seen in migrating and wintering flocks.

Habitat

• Breeds on subarctic and arctic tundra, near ponds or streams.
• Winters in coastal marshes and bays, wet grasslands, freshwater marshes, and cultivated fields.

Food

Entirely vegetarian. Eats variety of plant species and parts, from aquatic plants to grasses and grain.

Behavior

Courtship displays and pairing take place in spring, during a goose’s second spring migration. Pairs remain together for life. Feeds in water-logged soil or shallow water.

Conservation

Populations have been growing exponentially in most parts of the range. Some colonies are becoming so large that the geese are destroying nesting habitat, and hunting is proposed to decrease the populations.