Bird Migration Wonders

To learn more about extraordinary activities related to preparing for and undertaking migration, Audubon recently tracked down some information to answer some of the most frequently asked questions about migrating birds. Obviously, birds have super-skills far beyond human abilities: They depart on time without the use of a calendar or watch, and they navigate long distances without a smartphone or map. They fly for days with few, if any, rest stops. Their bodies undergo remarkable changes so they are in top shape to undergo long migration flights.
How do birds prepare their bodies for flight? Migrating is a major physical challenge for birds. To get ready, some birds can make huge changes in their bodies in a matter of days. Birds rely on fat to fuel migration flights, in contrast to humans who burn a lot of carbohydrates and sugars during exercise. Some birds double their body weight before migration by gorging on insects, berries, earthworms, or mollusks. Others increase the size of their flight muscles, charge up their metabolism, and even grow or shrink digestive organs to increase or lose weight.
For example, during a study of Gray Catbirds, University of Rhode Island physiologist and ecologist Kristen DeMoranville found catbirds’ flight muscles were larger during migration. And while the birds wintered in the tropics, their hearts were reduced in size; but they gained fat, perhaps in anticipation for the spring migration season.
Biologists like DeMoranville are working to understand what genes and proteins are responsible for such body-morphing abilities, using information from human medical research as a starting point. The results could signal which foods are crucial for birds’ migratory flights, which in turn could help conservationists identify and protect the most important sources for nutrition for various birds.
How do birds know when to migrate? Varied cues help birds decide when to start their migrations, explained University of South Carolina ornithologist Nathan Senner, including day length, temperature, rainfall, food availability, and body condition. Birds may also pay attention to social cues to decide when it’s time to leave wintering areas. Read more










