Research Interests
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 favored by intra-sexual selection and those favored
by inter-sexual selection.
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Representative Publications
Kroodsma D. E. and B. E. Byers. 1991. The functions of bird
song. American Zoologist, 31: 318-328.
Byers B. E. and D. E. Kroodsma. 1992. Development of two song types by Chestnut-sided
Warblers. Anim. Behav., 44: 799-810.
Byers, B. E. 1995. Song types, repertories and song variability in a population of
Chestnut-sided Warblers. Condor, 97: 390-401.
Byers, B. E. 1996. Geographic variation of song form within and between Chestnut-sided
Warbler populations. Auk, 113: 288-299.
Byers, B. E. 1996. Messages encoded in the songs of chestnut-sided
warblers. Anim. Behav., 52: 691-705.
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. and King, D. I. 2000. Singing by female Chestnut-sided Warblers. Wilson
Bulletin, 112: 547-550.
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.
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.
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.
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.
Byers, B. E. 2007. Extra-pair Paternity in Chestnut-sided Warblers is Correlated with Consistent
Vocal Performance. Behavioral Ecology, 18:30-136.
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