The metabolic cost of birdsong production.

The metabolic cost of birdsong production has not been studied in detail but is of importance in our understanding of how selective pressures shape song behavior. We measured rates of oxygen consumption during song in three songbird species, zebra finches (Taeniopygia guttata), Waterslager canaries (Serinus canaria) and European starlings (Sturnus vulgaris). These species sing songs with different acoustic and temporal characteristics: short stereotyped song (zebra finch), long song with high temporal complexity (canary) and long song with high acoustic, but low temporal, complexity (starling). In all three species, song slightly increased the rate of oxygen consumption over pre-song levels (1.02-1.36-fold). In zebra finches, the metabolic cost per song motif averaged 1.2 microl g(-1). This cost per motif did not change over the range of song duration measured for the four individuals. Surprisingly, the metabolic cost of song production in the species with the temporally most complex song, the canary, was no greater than in the other two species. In starlings, a 16 dB increase in sound intensity was accompanied by a 1.16-fold increase in the rate of oxygen consumption. These data indicate that the metabolic cost of song production in the songbird species studied is no higher than that for other types of vocal behavior in various bird groups. Our analysis shows that the metabolic cost of singing is also similar to that of calling in frogs and of human speech production. However, difficulties with measurements on freely behaving birds in a small respirometry chamber limit the depth of analysis that is possible.