Where to from here? Perspectives on steroid-induced and naturally-occurring singing in female songbirds

Abstract

In many species, male and female animals differ in the types and frequency of particular behaviors (e.g. reproductive behavior, parental behavior, etc.). These differences in behavior are quite often related to the neural and hormonal control of said behaviors. In the temperate zone it is commonly stated that male songbirds sing much more frequently and with much greater quality compared to their female counterparts. However, recent evidence has called these claims into question (Odom et al., 2014; Price et al., 2008; Webb et al., 2016). That said, neuroendocrine studies of song behavior have primarily focused on male birds and relatively little work has been done exclusively or comparatively with female songbirds. What we do know, however, is that there is wide variability in the vocal ability and capacity of female songbirds and that there is a developmental link between the hormonal milieu and neuro-social development that facilitate these behavioral phenotypes. Both testosterone and estradiol have been demonstrated to play pivotal roles in behavioral and neural differentiation of male and female song behavior profiles. Here we review a brief history of empirical investigation into steroid regulation of song in female birds, including the pattern of song activation, constraints on the ability of testosterone to induce singing, and the role of the anterior forebrain in supporting song learning. We conclude with a brief analysis of a major gap in the field's knowledge regarding naturally occurring female song and the neuroendocrine underpinnings of a socially salient learned behavior ripe for systematic investigation.

Keywords: Birdsong; Female song; Female songbird; Sex steroids; Testosterone.