Patterns of Response to Natural Stimulation and Reproductive Suppression in Mallards

Abstract

This study examined in mallards the onset of precopulatory behavior, the sequence and nature of peripheral blood changes, and the implied patterns of reproductive stimulation in response to endogenous estrogen stimulation and reproductive suppression. Continuous records were taken of seven serum parameters on 10 semidomesticated female mallard ducks as well as behavioral obser- vations and egg-laying records. Similar observations were made on daily changes during the laying period and on response to artificial suppression. Birds which responded early in the season demon- strated different patterns of development than those which appeared retarded. The onset of pre- copulatory behavior generally preceded blood changes by as much as 3 weeks. As the reproductive season progressed, the time necessary for the onset of physical response appears to have been mate- rially reduced. Subjection to a stressor (close confinement) did not result in regression of the re- productive system and release resulted in recovery as rapidly as 3 days. No well-defined differences between peripheral blood constituent levels of ovulatory and anovulatory groups were found at any specific time of the day. The mean values obtained, however, differed generally from results previously published. Abstract: This study examined in mallards the onset of precopulatory behavior, the sequence and nature of peripheral blood changes, and the implied patterns of reproductive stimulation in response to endogenous estrogen stimulation and reproductive suppression. Continuous records were taken of seven serum parameters on 10 semidomesticated female mallard ducks as well as behavioral obser- vations and egg-laying records. Similar observations were made on daily changes during the laying period and on response to artificial suppression. Birds which responded early in the season demon- strated different patterns of development than those which appeared retarded. The onset of pre- copulatory behavior generally preceded blood changes by as much as 3 weeks. As the reproductive season progressed, the time necessary for the onset of physical response appears to have been mate- rially reduced. Subjection to a stressor (close confinement) did not result in regression of the re- productive system and release resulted in recovery as rapidly as 3 days. No well-defined differences between peripheral blood constituent levels of ovulatory and anovulatory groups were found at any specific time of the day. The mean values obtained, however, differed generally from results previously published.