Prolactin in the Cowbird's Pituitary in Relation to Avian Brood Parasitism

Abstract

THE European cuckoo provides a familiar example of complete brood parasitism, that is, failure to build nests, coupled with the habit of laying eggs in the nest of other birds which generally take over incubation and hatching of the foreign eggs. This habit is also shown by the North American brown-headed cowbird (Molothrus ater) as well as other species. Birds showing brood parasitism do not develop brood patches. Bailey1 has shown that brood patch development in passerines requires the action of an œstrogen and of prolactin. Prolactin can also induce broodiness in pigeons and poultry.