SEASONAL-CHANGES OF THERMAL CONDUCTANCE IN ZONOTRICHIA-CAPENSIS (EMBERIZIDAE), FROM CENTRAL CHILE - THE ROLE OF PLUMAGE

Oxygen consumption and cooling curves of intact and defeathered rufous -collared sparrows (Zonotrichia capensis) from Central Chile were seas onally determined. The results obtained indicated that conductance val ues in Zonotrichia capensis are significantly lower during winter. Coo ling curves in intact birds compared with defeathered animals also sho wed different seasonal ratios. The increase in plumage insulation and the consequent decrease of thermal conductance during winter (quality of plumage) may be an important compensatory adjustment to minimize hi gher demands during cold conditions.