Snow geese pair for life and associate in flocks called gaggles. Simple nests are built on the ground. The rough-surfaced, whitish eggs are incubated for about a month by the hen while the gander stands guard. The downy young fend for themselves almost at once but remain with their parents during the first summer. Geese may survive for 10–15 years in the wild. These migratory birds winter in limited localities far south of their breeding grounds. Powerful and high-flying, they travel in V-formations to conserve energy by taking advantage of air currents (vortices) created by the wing tips. Both sexes utter loud honking or gabbling cries while on the wing or when danger appears. When angry, geese vibrate their neck feathers; after routing an intruder, the gander utters a triumphant note that is echoed by his mate and young goslings.