My research focuses on explaining the patterned complexity of songbird vocalizations. Songbirds produce sounds of unparalleled acoustic complexity, which they use in structured, behaviorally complex communication systems that vary tremendously among songbird species. The components of these communication systems are transmitted to succeeding generations by mechanisms both biological and cultural (i.e., by a combination of heredity and learning). Songbird singing is thus a fascinatingly complex, multidimensional trait that arose through the interplay of biological and cultural evolution. The trait as whole, extraordinarily intricate and intimately associated with reproduction, must be an adaptation. But a detailed understanding of exactly how singing affects fitness remains elusive. What processes have driven the evolution of the particular patterns of song production and performance that we observe in songbird species? Which particular features of singing are adaptive?
In practice, answering evolutionary questions about the adaptive value of singing behavior means investigating how songs function in the social lives of songbirds. By determining whether particular aspects of singing confer reproductive advantages on birds that use them, we can infer past and/or current selection. To investigate song function, I take several complementary approaches: 1) careful observation and description of songs and singing to identify meaningful patterns of variation; 2) searches for correlations between aspects of singing and components of fitness; 3) field experiments to test whether song features correlated with fitness do in fact serve a communicative function that could be selected; and 4) comparative studies to determine whether variability in song features among species is correlated with differences in ecology and life history; such correlations between behavior and environment can reveal adaptation.
One of the main difficulties in assessing the functions of male song features is distinguishing between the features selected for effective mate attraction and those selected for effective management of competition with other males. These two types of communication may require different song properties and singing behaviors, and many song systems may have evolved as compromise solutions to the demands of conflicting functions, making if difficult for investigators to disentangle the evolutionary contributions of the two types of communication. Therefore, my investigation of song function has focused mainly on the wood warblers (Parulidae), a group in which most species have song repertoires divided into two categories: one used mainly for within-sex communication and one used mainly for between-sex communication. Male-directed and female-directed songs have thus been free to evolve independently, and provide a superb opportunity to examine separately the features that have evolved for communication in aggressive contexts and those that have evolved for communication in mating contexts.
Byers, B. E., Akresh, M. E., and D. I. King 2020. Song learning by prairie warblers: When, where, and from whom. Ethology, 126:1079-1088.
Byers, B. E. 2017. Chestnut-sided warblers use rare song types in extreme aggressive contexts. Animal Behaviour,, 125:33-39.
Byers, B. E., Akresh, M. E., and D. I. King 2016. Song and male quality in prairie warblers. Ethology, 122:660-670.
Byers, B. E., Akresh, M. E., and D. I. King 2015. A proxy of social mate choice in prairie warblers is correlated with consistent, rapid, low-pitched singing.Behavioral Ecology and Sociobiology, 69: 1275-1286.
Byers, B. E. 2015. Migration and song elaboration in Geothlypis wood warblers. The Auk: Ornithological Advances, 132:167-179.
Kroodsma, D. E., Hamilton, D., Byers, B. E., et al. 2013. Behavioral evidence for song learning in the suboscine bellbirds (Procnias spp.; Cotingidae). Wilson Journal of Ornithology, 125:1-14.
Byers, B. E., Kramer, B. A., Akresh, M. E., and D. I. King 2013. Interspecific song imitation by a prairie warbler. Journal of Field Ornithology, 84:181-186.
Byers, B. E. 2011. Birdsong, migration and sexual selection: a skeptical view. Anim. Behav. 82:e1-e3.
Byers, B. E., Belinsky, K. L. and Bentley, R. A. 2010. Independent cultural evolution of two song traditions in the chestnut-sided sarbler . American Naturalist, 176: 476-489.
Byers, B. E. and Kroosdma, D. E. 2009. Female mate choice and songbird song repertoires. Animal Behaviour, 77: 13-22.
Byers, B. E. 2007. Extra-pair Paternity in Chestnut-sided Warblers is Correlated with Consistent Vocal Performance. Behavioral Ecology, 18: 30-136.
Byers, B. E., Mays Jr., H. L., Stewart, I.R.K. and D. Westneat. 2004. Extra-pair paternity increases variability in male reproductive success in the chestnut-sided warbler (Dendroica pensylvanica), a socially monogamous songbird. Auk., 121: 788-795.
King, D. I. and Byers, B. E. 2002. An evaluation of powerline rights-of-way as habitat for early successional shrubland birds. Wildlife Society Bulletin, 30: 868-874.
Gillihan, S. W. and Byers, B. E. 2001. Evening Grosbeak (Coccothraustes vespertinus). In The Birds of North America, No. 599 (A. Poole and F. Gill eds.). The Birds of North America, Inc. Philadelphia, PA.
Kroodsma, D. E., Byers, B. E., Goodale, E., Johnson, S., and W. Liu. 2001. Pseudoreplication in playback experiments, revisited a decade later. Anim. Behav., 61: 1029-1033.
Byers, B. E. and King, D. I. 2000. Singing by female Chestnut-sided Warblers. Wilson Bulletin, 112: 547-550.
Kroodsma D. E. and B. E. Byers. 1998. Songbird song repertoires: an ethological approach to studying cognition. Pages 305-336 in Animal Cognition in Nature. Academic Press.
Byers, B. E. 1996. Messages encoded in the songs of chestnut-sided warblers. Anim. Behav., 52: 691-705.
Byers, B. E. 1996. Geographic variation of song form within and between Chestnut-sided Warbler populations. Auk, 113: 288-299.
Byers, B. E. 1995. Song types, repertories and song variability in a population of Chestnut-sided Warblers. Condor, 97: 390-401.
Byers B. E. and D. E. Kroodsma. 1992. Development of two song types by Chestnut-sided Warblers. Anim. Behav., 44: 799-810.
Kroodsma D. E. and B. E. Byers. 1991. The functions of bird song. American Zoologist, 31: 318-328.