ON BROODINESS OF RING DOVES FOLLOWING IMPLANTS OF CERTAIN STEROID HORMONES

Abstract

Ring doves of both sexes and of 3 age levels were used to test the ability of implanted pellets of certain steroid hormones to induce broodiness and to release prolactin from the pituitaries of the treated birds. Seventeen untreated pairs of mature or adolescent doves served as controls and these, together with 5 pairs treated with pellets of estrone (total of 44 birds), did not become broody nor did their crop-sacs increase in size. Paired adult and adolescent birds of either sex treated with progesterone or DCA and similar [female][female] treated with testosterone propionate, became broody in 43 of 62 tests. Twenty-one of these broody birds were killed while broody, or while feeding young, and proof of enlargement of their crop-sacs was obtained by weighing these organs; a total of 29 of these responding birds fed or reared young, thus proving both the functional state of their crop-sacs and the antecedent release of prolactin under the stimulus of the effective steroids. These steroids were nearly or quite ineffective in young doves and in isolated (unpaired) mature doves. Those steroid hormones which were earlier observed by Riddle, Lahr, and Bates to promote maternal behavior in rats were here shown to be effective in inducing broodiness in doves. This effect in doves was produced by steroids which caused a concurrent release of prolactin from the dove''s own pituitary but not by steroids which failed to do so. This result provides further evidence for a specific role of prolactin in the initiation of broodiness and parental care.