Oxygen consumption in relation to ambient temperature in five species of forest-dwelling thrushes ( Hylocichla and Catharus)

Abstract

1. 1. The standard metabolic rates of five forest-dwelling thrushes ( Hylocichla mustelina, Catharus fuscescens, C. guttatus, C. ustulatus and C. minimus) resting in the dark at thermoneutrality during their normal active period averaged 14·8 per cent below values predicted by Aschoff & Pohl (1970) but were nearly identical to the values predicted by Lasiewski & Dawson (1967). 2. 2. Oxygen consumption of these five thrushes is a linear function of air temperature below speciesspecific lower critical temperatures. 3. 3. The only statistically significant difference ( P>0·95) between regression equations relating metabolism below thermoneutrality to ambient temperatures among the five species was that between C. minimus and C. ustulatus. 4. 4. The flatter slope exhibited by C. minimus may represent a metabolic adjustment to the more rigorous environment at high elevations which it alone inhabits.