Metabolic rate and colonic temperature were measured in chukars between 1st and 108th day of life (divided into six age groups: 1-3-days old, 1, 2, 3, and 4-weeks old and 3.5-months old) in ambient temperatures set separately for each group and ranging from -12 to 41 degrees C. The Gompertz growth constant for growing chukars (0.042) was close to the value obtained in earlier study for the grey partridge. Similarly as in other species of Galliformes, newly hatched chukar chicks had lower T(b) at TNZ (39.5 degrees C) than that found in older birds (41.3 degrees C in 4-weeks old). The body temperatures taken at TNZ in 2-weeks old chicks and older fitted neatly within allometrically predicted limits of body temperatures for adult birds. The values of RMR at TNZ followed closely a biphasic pattern, with the second phase correlating strongly with the body mass. The value of metabolic scope (the level of metabolic efficiency) for the youngest group was high (3.2) and exceeded the values obtained in earlier studies for other gallinaceous species, including the grey partridge. The obtained values of minimum wet thermal conductance for growing chukar chicks exceeded the predicted values by approximately 40% but the slopes of both lines were very similar. In chukars, the key stage in the expression of fully developed thermoregulatory capacities comes immediately after the first week of life (maintaining somewhat constant body temperature, evident drop in the value of RMR at TNZ and minimal thermal conductance). The model of gradual development of thermoregulation which could be derived from the experiments on chukar chicks was characteristic for typical precocial birds.