Although sound production requires energy, it has been unclear how much singing increases metabolic rate in passerine birds. We measured the rate of oxygen consumption of two breeds of canary that sang inside a respirometry chamber. Metabolic rate increased with the proportion of. time that birds spent singing. Average metabolic rate during singing at 15-20degreesC was 1.05-1.07 times that of standing quietly in the same temperature range or 2.2-2.6 times basal metabolic rate (BMR). Whether an increase in metabolic rate during song of this order would represent a fitness cost to free-living passerine birds would depend upon the circumstances. Singing rather than perching during the day would raise metabolic rate only slightly. Singing at night or at dawn, instead of sleeping with a metabolic rate closer to BMR, would cause a greater increase in metabolism. Birdsong could act as a condition-dependent signal, since birds that are easily able to achieve energy balance could afford the cost of singing, but those close to their energy limits might not. (C) 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
- nestling passerines
- sexual selection