The roles of stimuli from young, previous breeding experience, and prolactin in regulating parental behavior in ring doves (Stretopelia risoria)

In addition to stimulating crop "milk" formation in ring doves, prolactin ( PRL) may promote the parental regurgitation behavior that transfers this "m ilk" to the young at the time of hatching. Although earlier studies suggest that previous breeding experience is an important modulator of PRL-induced parental regurgitation behavior in ring doves, the ways in which experienc e, hormones, and stimuli from young interact to promote parental behavior h ave not been well characterized in this species. In the first study, untrea ted, nonbreeding female doves with and without previous breeding experience were given 10 daily parental behavior tests (2 h/day) with a hungry 5- to 10-day-old foster squab. Experienced females exhibited a higher incidence o f regurgitation behavior, defensive behavior, and crouching or sitting in t he nest than did inexperienced females. In a second study, nonbreeding fema les were given 10 daily tests for parental behavior while they received sc injections of ovine PRL or vehicle,. Prolactin reduced squab-directed aggre ssion and increased the incidence of regurgitation feeding behavior of fost er squabs in both experienced and inexperienced females. However, the avera ge number of regurgitation feeding acts displayed by those PRL-treated fema les that showed the behavior was over eight times higher in experienced fem ales than in inexperienced females. Previous experience also enhanced the s timulatory effects of PRL on defensive behavior and crouching or sitting in the nest. The parental behavior exhibited by nonbreeding, PRL-treated expe rienced females was qualitatively and quantitatively similar to that observ ed in normally breeding females during a single test with their own hungry 5- to 10-day-old squabs. These findings indicate that PRL and previous bree ding experience both enhance the parental responsiveness of nonbreeding fem ale doves and that under optimal hormonal, experiential, and squab exposure conditions, nonbreeding doves exhibit levels of parental activity that riv al those of normally breeding parents. (C) 1999 Academic Press.