Oxygen consumption rates were measured in chicks (0-17 days of age), and in non-brooding and brooding adults. Brooded chicks maintained a constant oxygen consumption rate at a chamber ambient temperature of 10-35 degrees C (0-5 days of age: 2.95 ml O2.g-1.h-1 and 6-17 days of age: 5.80 ml O2.g-1.h-1) while unbrooded chicks increased oxygen consumption rate at ambient temperature below 30 degrees C to double the brooded oxygen consumption rate at 25 and 15 degrees C for chicks < 5 days of age and > 5 days of age, respectively. The mass-specific oxygen consumption rate of breeding male and females (non-brooding) were significantly elevated within the thermoneutral zone thermal neutral zone (28-35 degrees C) in comparison to non-breeding adults. Below the thermal neutral zone, oxygen consumption rate was not significantly different. The elevation in oxygen consumption rate of breeding quail was not correlated with the presence of broodpatches, which developed only in females, but is a seasonal adjustment in metabolism. Male and females that actively brooded one to five chicks had significantly higher oxygen consumption rate than nonbrooding quil at ambient temperature below 30 degrees C. Brooding oxygen consumption rate was constant during day and night, indicating a temporary suppression of the circadian rhythm of metabolism. Brooding oxygen consumption rate increased significantly with brood number, but neither adult body mass nor adult sex were significant factors in the relationship between brooding oxygen consumption rate and ambient temperature. The proportion of daylight hours that chicks were brooded by parents was negatively correlated with ambient temperature. After chicks were 5 days old brooding time was reduced but brooding oxygen consumption rate was unchanged. Heat from the brooding parent appeared to originate mainly from the apteria under the wings and legs rather than the broodpatch. The parental heat contribution to chick temperature regulation below the chicks' thermal neutral zone is achieved by increasing parental thermal conductance by a feedback control similar to that suggested for the control of egg temperature via the broodpatch. It is concluded that the brooding period is an energetic burden to parent quail, and the magnitude of the cost increases directly with brood number and inversely with ambient temperature during this period.(ABSTRACT TRUNCATED AT 400 WORDS)