Effect of female sexual displays on the endocrine physiology and behaviour of male white‐crowned sparrows, Zonotrichia leucophrys

Abstract

In photoperiodic birds, endocrine responses to behavioural interactions between males and females may be involved in temporally “fine‐tuning” the onset of reproduction to yearly variations in the environment. This study examined the endocrine and behavioural responses of male White‐crowned sparrows (Zonotrichia leucophrys) to changes in the endocrine state of the female, as signalled by changes in her behaviour. Males on different photoperiodic regimes were paired with oestrogen‐treated, sexually receptive females. Males exposed to gonadostimulatory long days mounted and copulated with oestrogen‐treated females even before gonadal development was complete. These males had higher plasma levels of testosterone and luteinizing hormone and maintained enlarged testes longer than control males paired with untreated, nonreceptive females. Males maintained on nonstimulatory short days also mounted oestrogen‐treated females; however, testes of these males remained nonfunctional and their plasma levels of testosterone and luteinizing hormone were basal. Thus, reproductive function of photostimulated males is profoundly affected by changes in the endocrine state and behaviour of the female. However, male sexual behaviours are expressed in response to visual and auditory stimuli from the female regardless of male hormonal condition or photoperiodic treatment.