It’s no surprise that birds lose fat during migration, but the loss of muscle mass, even when there is still fat to burn, has been a puzzle. A paper in the Sept. 9 issue of the journal Science shows that by metabolizing muscles and organs, the birds gain water.

In wind tunnel tests with Swainson’s thrushes, the researchers found that, even flying hard with no water to drink, the birds maintained their water balance in very dry conditions.

Read the paper in Science (fee or subscription required), here.

Or read the promotional blurb from the journal announcing the paper here.

NPR covered the story, as did the Los Angeles Times.

Photo: Swainson’s thrush, courtesy National Park Service