At these lakes they encounter young, non-breeding birds of the previous year and unsuccessful nesters or unpaired adults that have spent the summer in small groups in favourable feeding locations. From these points, the flocks begin the early stages of migration as freeze-up approaches. An early winter will doom cygnets not yet ready to fly out of the north. Even after they have returned to the wintering range, birds of the eastern population in the northern part of Chesapeake Bay may face a prolonged freeze in a severe winter. Rather than heading south to more temperate conditions, they sometimes spend most of this time sleeping on the ice, their heads drawn back under their wings.
Many birds often die, particularly young birds.
Food Tundra Swans feed mainly on the tubers and roots of aquatic plants that grow at shallow depths in fresh, brackish, or salt water. They reach this food by extending the head and neck downward, frequently tipping the body but seldom completely submerging. On the Atlantic coast the swans vary their diet with mollusks, such as mussels and clams. In recent years, they have begun to feed extensively on grains, such as corn and wheat, that are left on the ground after the harvest. Management Tundra Swans have few natural enemies other than humans.