Birds
Goose
Anserinae · also called geese
A goose is the middle child of the waterfowl family — bigger and longer-necked than a duck, smaller and shorter-necked than a swan, and more committed to grazing on dry land than either. It migrates in the familiar V, mates for years, and, when it has goslings to protect, is one of the few birds that will genuinely come at a person.
Overview
Geese are the waterfowl subfamily Anserinae (shared with the swans), around 20 species, almost all in the Northern Hemisphere. They have medium necks, forward-set legs for walking, and, unlike most ducks, no strong plumage difference between the sexes. All are grazing herbivores, feeding on grass, sedges, grain, and crops far more than they feed in the water.
Flying in formation
Migrating geese fly in a V or diagonal line so each bird rides the rising air coming off the wingtip of the bird ahead, cutting the effort of flight. They rotate the unaided lead position and seem to time their wingbeats to catch the lift.
Family life
Geese pair for years, often for life, and both parents escort the goslings through the first migration. Newly hatched geese imprint on the first large moving thing they see — normally the mother — the behaviour Konrad Lorenz demonstrated by having goslings follow him. Each summer a goose moults all its flight feathers at once and is grounded for weeks, staying near open water.
City geese
The Canada goose and greylag, once long-distance migrants, have formed large non-migratory populations on parks, golf courses, and reservoirs, where mown grass, open water, mild winters, and feeding remove any reason to move.
Status
Geese as a group are Not Evaluated. Most northern species are abundant or increasing, some to the point of causing crop and ecological problems, but the swan goose of East Asia is Critically Endangered, the Hawaiian nene recovered from about 30 birds in the 1950s, and the red-breasted goose depends on a few wintering sites.
Goose: common questions
Why do geese fly in a V?
The V-formation is an energy-saving arrangement. As a goose flaps, its wingtips throw off a swirl of air with a rising component just outside and behind each tip. By positioning itself slightly behind and to the side of the bird in front, a following goose sits in that band of rising air and gets some free lift, so it can fly with less effort and a lower heart rate. The birds also seem to time their wingbeats to make the most of the moving air. The lead bird gets no such help, so geese take turns at the front, and the honking is thought partly to help maintain position and coordination.
What is the difference between a goose, a duck, and a swan?
All three are in the waterfowl family Anatidae and grade into one another by size and proportion. Swans are the largest, with very long necks and, in the northern species, all-white adult plumage. Geese are intermediate, with medium necks, stout forward-set legs for walking and grazing on land, no strong plumage difference between the sexes, and long pair bonds with biparental care. Ducks are the smallest and most varied, with short necks, and in many species males and females look very different, with the female usually raising the brood alone. There is no sharp boundary, and a few birds sit awkwardly between the categories.
Why are geese so aggressive?
Geese are large, they nest on the ground where eggs and goslings are vulnerable, and both parents invest heavily in a small number of young, so natural selection favours birds that defend the nest and family boldly. A defending goose lowers its head, hisses, spreads its wings to look bigger, and will charge, bite, and beat with the wrists of its wings, which can bruise and knock over a person or a dog. This is almost entirely a breeding-season behaviour, from roughly the start of nesting until the goslings can fly. Outside that period geese are wary and will simply move away. Giving nesting geese a wide berth resolves nearly all conflict.
Why do city parks have so many Canada geese?
A park is close to ideal goose habitat. Short mown grass beside open water is exactly what a grazing goose wants, the water offers safety and a place to moult, there are few natural predators, winters in many cities are mild enough that the birds no longer need to migrate, and people often feed them. Canada geese introduced or resident in the northern United States, parts of Canada, and Europe have taken full advantage, forming large non-migratory flocks that breed on the spot. The droppings, grazed turf, and aggressive nesting birds that result are a common source of complaint, managed with habitat changes, deterrents, and egg control rather than easily reversed.