By Susan Milius
The first measurements of energy use in migrating songbirds have confirmed a paradox predicted by some computer models of bird migration: Birds burn more energy during stopovers along the way than during their total flying time.
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Martin Wikelski of Princeton University and his colleagues monitored 38 Swainson’s and hermit thrushes during the nights of their spring migration through the northern United States. The researchers injected the radio-tagged birds with chemical-isotope tracers that enabled the scientists to measure the birds’ metabolism. The team members spent their nights driving a car, trying to keep up with a tagged bird. “We got stopped by a cop just about every night, not because we were speeding, but because they wanted to know what somebody was doing in a little town in Wisconsin at 4 a.m. with a giant antenna on the roof of a car,” says Wikelski.