With the facts as given in this article, the birds spent about 7 percent of their time flying and 93 percent not flying. At the energy rates given, I get that 25 percent of the energy used was spent during the 7 percent of time the birds were flying. The article appeared to state that somehow flying was more energy-efficient than resting, but the flight portion measured was only 4.6 hours long and the nonflight days were 24 hours long, so they weren’t comparable.

Elizabeth Oscanyan
Philomont, Va.

Your facts are right, but this study looks at energy budgets, not energy efficiency. The total energy spent at stopovers was greater than the total spent flying .–S. Milius