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Snow goose

life science Maturity 7-9 Next article →

The snow goose, known scientifically as Anser caerulescens, is a large bird native to North America. These geese are famous for their striking appearance and their massive migrations across the continent. They play a major role in the ecosystems of both the Arctic tundra and warmer southern lands. Understanding these birds helps scientists learn how changes in land use can affect wildlife populations. They are closely related to Ross's goose, which is known as their sister species.

Snow goose taking off at Gray Lodge Wildlife Area-0058
Snow goose taking off at Gray Lodge Wildlife Area-0058

Snow geese come in two distinct color phases, often called "snows" and "blues." The white morph is mostly white with black wing tips. The blue morph has bluish-gray plumage, though its head, neck, and tail tip remain white. These colors are controlled by genetics. A single dominant gene creates the dark blue phase. The white phase occurs when a bird is homozygous recessive. While they look different, they are the same species and will interbreed.

There are two recognized subspecies based on their size and where they live. The lesser snow goose, or Anser caerulescens caerulescens, is the smaller version. It breeds in places like northeast Siberia, north Alaska, and northwest Canada. It winters in the southern United States, Mexico, and even Japan. The greater snow goose, or Anser caerulescens atlanticus, is slightly larger. This subspecies nests further north and east in northeast Canada. Both subspecies have pink bills with black edges called tomia. These black edges create a look often described as a "grin patch."

Snow goose taking off at Gray Lodge Wildlife Area-0058
Snow goose taking off at Gray Lodge Wildlife Area-0058

History shows how humans have documented these birds for centuries. In 1750, the English naturalist George Edwards described them as "the blue-winged goose." He used a hand-colored etching based on a specimen from Canada's Hudson Bay. In 1758, the Swedish naturalist Carl Linnaeus gave them the formal name Anas caerulescens. Later, in 1760, the French zoologist Mathurin Jacques Brisson introduced the genus Anser. This is the genus snow geese belong to today. The specific name "caerulescens" comes from the Latin word for "bluish."

Snow goose taking off at Gray Lodge Wildlife Area-0058
Snow goose taking off at Gray Lodge Wildlife Area-0058

Life cycles for snow geese involve strong social bonds and careful nesting. Most geese form long-term pair bonds during their second year of life. They usually begin breeding in their third year. Females are philopatric, which means they return to the exact place they hatched to breed. They often build nests in large colonies on high ground. A female lays between three and five eggs and protects them for 22 to 25 days. Once the young hatch, they can fly after 42 to 50 days. They stay with their parents for up to three years.

Snow goose taking off at Gray Lodge Wildlife Area-0058
Snow goose taking off at Gray Lodge Wildlife Area-0058

Migration is a massive undertaking that takes up more than half of their year. In the spring, they follow narrow corridors known as flyways. The lesser snow goose uses the Central, Mississippi, and Pacific Flyways. They move across prairies and farmland to reach the Gulf coastal plain. The greater snow goose uses the Atlantic Flyway. Traditionally, they ate marsh grasses, but many have shifted to eating grain in agricultural fields. This change in diet may be why their population has grown so quickly. In 2015, a disease called avian cholera killed 2,000 geese during their migration in Idaho.

Snow goose taking off at Gray Lodge Wildlife Area-0058
Snow goose taking off at Gray Lodge Wildlife Area-0058

The population of lesser snow geese has grown tremendously. There are now more than 5 million breeding birds. This is an increase of over 300% since the mid-1970s. Their numbers are rising by more than five percent every year. This rapid growth can cause problems like overgrazing in the Arctic. Large numbers of geese can damage the tundra and saltmarshes. To help, the Light Goose Conservation Order was established in 1997. This helps manage the population to protect the natural habitats they rely on.

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