A Use of Fat

The long-distance flights of birds are renowned. But how can birds fly such great distances nonstop? What do they live on, inasmuch as scientists conclude that a flying bird uses six to eight times as many calories as a bird at rest?

Basically the fuel for such flights is fat. Prior to migration, the bird undergoes a change in metabolism; so it begins to store large quantities of fat. On a blackpoll netted just before its long overwater flight, half the bird’s weight was stored fat. So when these migrating birds take off they are bulging with layers of fat, “fuel” for their flight.