Abstract
The white-crowned sparrow, Zonotrichia leucophrys gambelii, has been shown to become hyperphagic, deposit fat, and gain weight prior to the vernal migration. Similar effects have been induced during the winter by artificially increasing the duration of the daily photoperiod. It appears that the mechanism involved in these photoperiodically induced changes in metabolism may include the hypothalamus, and possibly also the anterior pituitary. In the investigation reported herein, it was possible to induce similar changes with exogenous hormones. Prolactin promoted a rapid fat deposition that was reflected in conspicuous daily increments in body weight. Gonadotropin, alone, was ineffective but was synergistic with prolactin in promoting an increase in lipid reserves. These effects were obtained in winter with photosensitive birds as well as in summer with photorefractory birds.
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