Anser caerulescenssnow goose

Geographic Range

Anser caerulescens have quite an expansive geographical range. They leave their wintering grounds in March and head north over the New England states. They rest between the first week in April and the end of May in the St. Lawrence River area. They then continue northward over central Quebec, Canada to their destination in the northeast artic. The breeding grounds cover the area from northern Baffin Island, west to Bathurst Island, north to Alert on Ellesmere Island, and east to northwest Greenland. The southwest coast of Bylot is the location of the main nesting colony. They leave their breeding grounds in September. They begin to arrive at the St. Lawrence River area in October and stay until early November when they continue to their American wintering grounds(Heyland, 2000). Their main wintering grounds are along the gulf coast of Louisiana and Texas between the Mississippi delta and Corpus Christi, Texas. However, in recent years colonies have been seen in Missouri, Illinois, Kansas, Oklahoma, Nebraska, and Iowa. Smaller numbers are found in eastern Mexico and southern New Mexico (Belrose, 1942). (Belrose, 1976; Heyland, 2000)

Habitat

The breeding grounds of Anser caerulescens consist of low grassy tundra with flat basins within 10 km of lakes, rivers, flood plains, or seas. Some choose rockier terrain near grassy wet tundra and flat marshy areas protected from the north by mountains. Overall they prefer coastal lagoons, marshes, tidal flats, and estuaries, but have been known to take advantage of prairies and agricultural lands. (Ehrlich, et al., 1988)

Physical Description

Anser caerulescens stand 63.5 to 78.7 cm tall (and average 70 cm in length) with wing lengths varying from 400 to 450 mm. They weigh from 2 to 3 kg. Males and females are similar in appearance although males are usually larger. There are two phases seen in Anser caerulescens called the "snow" phase and the "blue" phase. In the adult "snow" phase the body is a snowy white with black wing tips. They have red feet and legs, a pink bill, and a black "grin patch" (the black patch of skin that surrounds the base of the bill, which resembles a smile). The adult blue phase geese have the same feet, legs, bill, and grin patch, but they have blue/gray bodies with black wing tips. They also have white necks and heads, and some white on the underside of their bellies. In the immature snow phase the body is a dirty white color with black wing tips and in the immature blue phase they are a slate gray with little or no white. In both immature phases they have red feet and legs but they are not as bright as the adult goose. It was once thought that the two different color phases were different species, but they are not. They interbreed with one another, and they are found together through out their geographical ranges. The colors are genetically controlled and when selecting mates they tend to choose a mate that resembles their parents. Individuals with a mixed set of parents will breed with either color phase. (Frerichs, 1997; Hebert, 2002)

  • Sexual Dimorphism
  • sexes alike
  • male larger
  • Range mass
    1606 to 3307 g
    56.60 to 116.55 oz
  • Average length
    70 cm
    27.56 in

Development

There are three stages of development in Anser caerulescens. There are the hatchlings and young, the juvenile non-breeders, and the adult breeders. The young grow rapidly and are fully fledged within forty-five days. They reach maturity in two years, which is when they usually pair up in a monogamous relationship with another Snow Goose. The pair begins to breed for the first time in June of the third year (Belrose 1976).

Reproduction

Anser caerulescens are monogamous and usually form long-term pair bonds. (Ehrlich, et al., 1988)

Anser caerulescens actually mate with their monogamous partners during their migration back to the artic tundra. Nesting occurs in June; nesting colonies can number in the tens of thousands. The geese begin building nests approximately ten days after arriving at the nesting site. They usually make shallow depressions in the ground and line them with bits of dry vegetation and down from the mother. The female will lay one egg a day until she reaches a full clutch of about 3 to 5. The eggs are incubated for 23 to 25 days while the male guards the nest and the mother. Young fledge in 45 to 49 days. Females reach sexual maturity between 2 and 4 years. Snow geese tend to nest near snowy owls, which are believed to deter predators from coming to the nests. (Belrose, 1976; Ehrlich, et al., 1988; Tremblay, et al., 1997)

  • Breeding season
    From April to June
  • Range eggs per season
    1 to 6
  • Average eggs per season
    3-5
  • Average eggs per season
    4
    AnAge
  • Range time to hatching
    23 to 25 days
  • Range fledging age
    45 to 49 days
  • Range age at sexual or reproductive maturity (female)
    2 (low) years
  • Average age at sexual or reproductive maturity (female)
    4 years

Young snow geese are precocial and receive parental care from both the male and female parent. (Ehrlich, et al., 1988)

  • Parental Investment
  • no parental involvement
  • precocial
  • pre-fertilization
  • pre-hatching/birth
    • protecting
  • pre-weaning/fledging
    • provisioning
      • male
      • female

Lifespan/Longevity

The actual lifespan of Anser caerulescens is unknown, however, it is believed they have quite long lifespans. It was reported in one case that a goose was banded in 1957 and killed fifteen years later by a hunter. Annual mortality is between 25 to 50 percent and depends on age and breeding status. (Hebert, 2002; Heyland, 2000)

Behavior

Anser caerulescens are migratory birds that travel all the way from the northeast of Canada to the Gulf of Mexico and back. They travel in large flocks made of many family units and fly during both night and day. They tend to return to the same nesting areas year after year. During nesting the Geese break up into monogamous pairs. Both parents guard the brood, but the female does most of the brooding of the young. When taking the broods away from nest site females tend to group together in family packs. The males are territorial toward other males, and the females toward other females (Belrose, 1976). They usually nest in colonies, but some nest individually. They have been seen nesting near snowy owl nests, which is likely a solution to predation. Their nesting success was much lower when snowy owls were absent, which lead scientists to believe that the owls, since they are predatory bird, were capable of keeping predators away from the nests (Tremblay et al., 1997). (Belrose, 1976; Tremblay, et al., 1997)

Home Range

We do not have information on home range for this species at this time.

Communication and Perception

Anser caerulescens are known for their loud squawking and honking but no real studies have been done to determine the meanings, if any, of their vocalizations. (Hebert, 2002)

Food Habits

Anser caerulescens are herbivorous; they eat roots, leaves, grasses, and sedges. They have strong bills for digging up roots in thick mud. Their most common food source in the northern breeding grounds is American bulrush. As they migrate south they feed on the aquatic vegetation in wetlands and estuaries. They also forage in agricultural fields for wasted oats, corn and winter wheat. They eat tender shoots as they come up or feed on grass, weeds, and clover. In their Louisiana wintering grounds they feed on wild rice. Snow geese also need some sort of grit such as sand or shell fragments to aid in their digestion.

Foods eaten include: saltgrass, wild millet, spikeruch, feathergrass, panic grass, seashore paspalum, delta duckpatato, bulrush, cordgrass, cattail, ryegrass, wild rice, berries, aquatic plants and invertebrates, and agricultural crops. (Belrose, 1976)

  • Animal Foods
  • insects
  • Plant Foods
  • leaves
  • roots and tubers
  • seeds, grains, and nuts
  • fruit

Predation

Major predators include artic foxes (Vulpes lagopus) and gull-like birds called jaegers (genus Stercorarius). The biggest threat occurs during the first couple of weeks after the eggs are laid and then after hatching. The eggs and young chicks are vulnerable to these predators, but adults are generally safe. They have been seen nesting near snowy owl nests, which is likely a solution to predation. Their nesting success was much lower when snowy owls were absent, which lead scientists to believe that the owls, since they are predatory bird, were capable of keeping predators away from the nests (Tremblay et al., 1997). (Heyland, 2000; Tremblay, et al., 1997)

Ecosystem Roles

Anser caerulescens are considered to be overabundant and as a result have been stripping their habitat of its vegetation. (Heyland, 2000)

Economic Importance for Humans: Positive

Because of their large numbers the snow geese are hunted, although there are restrictions in place in order to protect the species from over hunting.

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

In recent decades many snow geese have become agricultural pests. They sometimes opt for easy food supplies found in farm fields with tender shoots and wasted corn, wheat, and oats. (Heyland, 2000)

  • Negative Impacts
  • crop pest

Conservation Status

The population size of Anser caerulescens is increasing at an estimated rate of 130,000 birds per year. Periodic hunting seasons have been established to help curb the growing population. There are restrictions, however, that protect snow geese from overhunting and efforts have been made to protect critical habitat in Canada and the United States. (Hebert, 2002; Heyland, 2000)

Contributors

Alaine Camfield (editor), Animal Diversity Web.

Jessica Logue (author), Western Maryland College, Randall L. Morrison (editor), Western Maryland College.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

herbivore

An animal that eats mainly plants or parts of plants.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

polymorphic

"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

References

Belrose, F. 1976. Ducks, Geese and Swans of North America. Harrisburg, PA: Stackpole Books.

Ehrlich, P., D. Dobkin, D. Wheye. 1988. The Birder's Handbook: A field guide to the natural history of North American birds. New York: Simon & Schuster Inc.

Frerichs, T. 1997. Lesser Snow Goose. Columbia, SD: U.S. Fish and Wildlife Service.

Hebert, P. 2002. "Snow Goose, Chen caerulescens" (On-line). Canada's Aquatic Environments. Accessed January 28, 2004 at http://www.aquatic.uoguelph.ca/birds/speciesacc/accounts/ducks/caerules/account.htm.

Heyland, J. 2000. "Canadian Wildlife Service. Greater Snow Goose" (On-line). Accessed April 9, 2002 at www.cws-scf.ec.gc.ca/hww-fap/greatsg/gsgoose.html.

Tremblay, J., G. Gauthier, D. LePage, A. Desrochers. 1997. Factors affecting nesting success in Greater Snow Geese: Effects of habitat and association with snowy owls. Wilson Bulletin, 109: 449.