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Research
Phylogenetic comparative studies of sex differences in birdsong
Classically, birdsong is thought to be sexually selected in males. However, comparative analyses by my colleagues and I revealed that female song is ancestral and widespread in songbirds. This means that birdsong originally evolved in both males and females. Furthermore, the absence of song in females of many songbird species is because females lost song in these species; not that elaborate song was solely gained in males. Through continued phylogenetic comparative analyses, we recently showed that female birdsong evolved in year-round territorial species with bi-parental care and was subsequently lost in many migratory lineages, resulting in the extreme variation seen in male and female song today. The important factors promoting song in both sexes appear to be monogamy, bi-parental care, cooperative breeding and year-round territoriality. Figure from https://www.nature.com/articles/s41467-025-60810-5
Integrative field studies on seasonal changes in song
Understanding how environmental and social cues lead to variation in male and female song within an individual's lifetime can help us pin-point the adaptive mechanisms leading to these behaviors. To do this, I investigate seasonal changes in male and female singing behavior. During my Ph.D. I showed that female troupials (a tropical oriole) sing consistently between the breeding and nonbreeding season whereas males sing most at dawn during the breeding season. This suggests that both social and sexual selection pressures are shaping sex-specific behaviors in this tropical species.
The SONG Lab is currently examining hormone regulation of male and female song rates in house wrens throughout the breeding season. In temperate songbirds, large increases in male singing early in the breeding season are associated with increased circulating concentrations of testosterone. However, we are finding that female house wren testosterone concentrations are very low throughout the breeding season, despite a peak in female singing during egg laying. We are currently investigating alternative explanations for this peak in female house wren song, including the role of other steroid hormones and increased neural sensitivity to testosterone in females. Figure modified from https://doi.org/10.1093/ornithology/ukag006
Neuroendocrine regulation of sex differences in song
Dr. Odom's SONG Lab also explores how neuroanatomy, hormone profiles, and gene expression interact to lead to differences in male and female song in wild songbirds. To do this, we are comparing changes in neuroanatomy, steroid hormone concentrations, and gene expression between the breeding and non-breeding season in female and male house wrens. These results help us understand how genes and hormones up and down regulate seasonal changes in male and female song. This also helps us understand how environmental variation can lead to increases or decreases in female song. Our goal is to eventually understand how these mechanisms contribute to the major sex differences in song and neuroanatomy we see in some species.
Using machine learning to quantify & detect female and male birdsong
My colleagues and I have been working on machine-learning approaches to quantify and compare birdsong across species. Our methods include using unsupervised random forest to classify song structure and determine the overlap in acoustic structure between sexes or species. In addition to publications describing these methods, we have made them readily available in the R package PhenotypeSpace. We also created a deep learning algorithm to classify female and male house wren songs within hours-long passively collected recordings. Check out this publication here: https://brill.com/view/journals/beh/162/10-11/article-p709_3.xml
