Snow Goose

• GeneralIt migrates in flocks of hundreds of thousands that turn the sky white.
• The colour morph is controlled by a single genetic locus in which the dark allele is incompletely dominant over the white.
• The breeding colonies of the dark morph were not discovered until 1929, after a deliberate search by Dewey Soper that lasted six years and covered more than 48,000 km.
• The two morphs remained almost allopatric until 1930; since then sympatry has produced gene flow, and hence the present pattern of colour frequencies.

Skeleton type

Vertebrate - internal bony skeleton (bird)

Habitat & environment

Arctic tundra; saltmarsh and farmland in winter

Birth weight

Precocial: born covered in down and leaves the nest within a few hours

Size at birth

Precocial: born covered in down and leaves the nest within a few hours

Sexual maturity

2-3 years

Gestation / incubation

22-25 days of incubation

Litter / clutch size

It is sociable even in the breeding season, and pairs nest very close together

Sources consulted: IUCN Red List (BirdLife International 2012); Birds of the World (Cornell Lab); Soper 1930, Canadian Field Naturalist 44; Cooke et al.; Bernis et al. 1994, Ardeola (nombres castellanos SEO); Linnaeus 1758; Kennard 1927

Best time: Winter in the southern United States and Mexico; it breeds in summer on the Arctic tundra