That's on par with measurements in other species. Franz Goller, a physiologist at the University of Utah, has studied the energetic costs of singing in birds. He guessed it would be tiring: A canary erupts in 30-second bursts of song, replete with complicated trills that require rapid "mini breathing," tens of times per second. When he ran experiments on zebra finches, though, which have comparable vocal behavior, he found their metabolic rates went up by only 5 to 35 percent while singing. That's about as tiring as cleaning one's feathers. Or, in human terms, Goller speculates, walking down the street.