Beyond a biased binary: A perspective on the misconceptions, challenges, and implications of studying females in avian behavioral endocrinology

Abstract

For decades, avian endocrinology has been informed by male perspectives and male-focused research, leaving significant gaps in our understanding of female birds. Male birds have been favored as research subjects because their reproductive behaviors are considered more conspicuous and their reproductive physiology is presumably less complex than female birds. However, female birds should not be ignored, as female reproductive behavior and physiology are essential for the propagation of all avian species. Endocrine research in female birds has made much progress in the last 20 years, but a substantial disparity in knowledge between male and female endocrinology persists. In this perspective piece, we provide examples of why ornithology has neglected female endocrinology, and we propose considerations for field and laboratory techniques to facilitate future studies. We highlight recent advances that showcase the importance of female avian endocrinology, and we challenge historic applications of an oversimplified, male-biased lens. We further provide examples of species for which avian behavior differs from the stereotypically described behaviors of male and female birds, warning investigators of the pitfalls in approaching endocrinology with a binary bias. We hope this piece will inspire investigators to engage in more comprehensive studies with female birds, to close the knowledge gap between the sexes, and to look beyond the binary when drawing conclusions about what is ‘male’ versus ‘female’ biology.

Repeated behavioral evolution is associated with targeted convergence of gene expression in cavity-nesting songbirds

“…This provides a unique opportunity to include both sexes in analyses of behavioral evolution. After all, females and males share the majority of their genome, yet sex-specific selective pressures can alter gene expression (27) and hormone secretion (28), which together may shape aggression or the mechanisms that promote the expression of aggression, the latter of which is still remarkably understudied in females (29,30). Critically, in both sexes, aggression shapes access to resources and mates, and the degree of such competition varies among species (25,26).…”

Journal of Zoology: The year in review

“…1). While the pattern is correlative, evidence suggests that diverse perspectives enhance innovation, which increases the impact of research (Riebel et al., 2019; Smiley et al., 2022). Thus, the Journal of Zoology is committed to enhancing and encouraging diversity, and breaking down barriers to successful research.…”

Androgen-armoured amazons: reversed sex roles in coucals are associated with testosterone in females but not males

“…Even if absolute concentrations of sex steroids are not reversed between females and males of sex-role-reversed species, females of such species may still express higher levels of testosterone than females of species with other mating systems. So far, comparative analyses of published testosterone data did not find any evidence for such a pattern [31,33,[52][53][54], but there is also a paucity of hormone studies in females [55,56]. Similarly, males of classically polyandrous species might express lower levels of testosterone than males of species with other mating systems, since they are the only parental care providers and high levels of testosterone have been shown to suppress paternal care (summarized by [57,58]).…”