Thyroid and gonad in the oxidative metabolism, erythropoiesis, and light response of the migratory redheaded bunting, Emberiza bruniceps

Abstract In the thyroidectomized, adult male redheaded bunting exposed to a L D cycle of 15 09 , there were no significant changes in body weight, gonad size, respiratory rates of whole body, liver, muscle, red blood cell number, hemoglobin concentration, or hematocrit, unlike in intact birds. Further, while testosterone appeared as effective as l -T 4 in determining body weight, gonadal size, and activity and oxygen uptake by skeletal muscle, it was of greater significance for kidney respiration and of secondary importance in its influence on blood morphology and respiratory rates of the liver and of the whole body of the bird.