Relatively difficult to identify, geese are perhaps
best known for their migration, being
harbingers of both summer and winter. Geese live
comfortably at the intersection of water and land,
eating a vegetarian diet of grasses, seeds, roots,
berries, and aquatic plants. Unlike many birds,
geese pair-bond and mate for life, building a simple
nest in the ground and lining it with down. Depending
on their species, geese lay a clutch of four
to nine eggs, and fledglings remain grounded for
forty to seventy-three days. Geese molt once a
year after the breeding season; during this period
the bird is unable to fly for four to five weeks.
Physical Characteristics of Geese
Geese are medium- to large-sized birds, between the size of ducks and swans. They have long necks and short legs in the center of their bodies. Because of this leg placement, geese do not waddle as much as other waterfowl when moving about on land. Their feet are webbed, which enables them to swim rapidly. The bills of geese have serrations on the mandibles called lamellae; these are useful, because most geese gather some of their food while submerged. Because the bill is equipped with a horny covering at the tip of the upper mandible and because of the curved shape of the bill, geese can easily clip grasses, grains, or other foods. Most species of geese are blackish in color, although many species have considerable white markings in their plumage, often restricted to their bellies or lower tail coverts. Even though each species has distinguishing physical characteristics, it is often difficult to identify a particular species in the field. Even Canada geese, which are probably the easiest to identify with their white chin straps, can be a source of frustration for bird watchers attempting to distinguish between the dozen or so subspecies of Canada geese. Male and female geese of each species resemble each other.
Many species of birds migrate, but geese, because they are so visible, epitomize this phenomenon to most people. Geese migrate for survival: Their northern breeding grounds become inhospitable when water areas freeze over, making food unattainable, and their southern grounds cannot sustain large populations of birds year around. In the United States, geese migrate northward fromFebruary to March and southward fromSeptember to November. Geese, likemanybirds, often return to the same summer and winter areas year after year. Clearly, geese make use of visual landmarks when migrating; even at night some landmarks, such as large bodies of water, can be seen from the air. Young geese learn about these landmarks, as well as about traditional migratory stopping places, from their elders. Landscape alone, however, is not all that helps geese navigate. The position of the sun and stars can help them, as can the wind and the earth's magnetic field. Most species of geese fly in some sort of Vformation. Flocks of snow geese, for example, form U's, checkmarks, or irregular masses. Only Canada geese fly in an almost perfect V. These formations have less to do with aesthetics than aerodynamics. Just as bicycle racers will draft lead bikers by riding slightly behind and to the side of them, so a goose will draft the lead bird, the one doing most of the work by breaking the wind's resistance for the birds that follow. Lead birds change during a flight. Geese normally fly at about forty miles per hour, a speed that can change if the bird is in a hurry or being chased. By plotting the origins and destinations of banded birds, biologists have discovered four main flyways used by geese in the United States: the Atlantic Flyway, the Mississippi Flyway, the Central Flyway and the Pacific Flyway. Banding geese in order to study them is more than an academic exercise. Knowing migration paths has allowed experts to make decisions on hunting quotas and on the location of wildlife refuges.
Tribe: Anserini (swans and geese, four genera, thirty-six species)
Geographical location: Primarily the Northern Hemisphere
Habitat: Land (fields, prairies, tundra, forests) and water (ponds, lakes, rivers, streams, inlets, tidal areas, oceans)
Gestational period: From three to four weeks
Life span: Most geese live about twenty years; can (rarely) reach fifty-five years
Special anatomy:Webbed feet, long necks, large bills
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