Sexual dimorphism and species differences in HVC volumes of cowbirds

Mark E. Hauber, Alex Kacelnik, Timothy J. DeVoogd, Nicola S. Clayton, Juan C. Reboreda

Research output: Contribution to journalArticlepeer-review


Cowbirds exhibit extensive variation in their social, territorial, and reproductive behaviors. Nissl-stained brain sections of specimens from a previous study (J. C. Reboreda, N. S. Clayton, and A. Kacelnik, 1996) were used to study the gross anatomy of a song control nucleus in 3 South American cowbirds (bay-winged, Molothrus badius; shiny, M. bonariensis; and screaming, M. rufoaxillaris). Cowbird high vocal center (HVC) volumes were consistently higher in males than in females in all 3 species. The largest HVC size of females found in bay-winged cowbirds is consistent with observations that females of this species, but not of the other 2 species, occasionally sing. The extent of the sexual dimorphism of relative HVC size was highest for the sexually dichromatic and promiscuous shiny cowbirds and smaller for the monochromatic and monogamous bay-winged and screaming cowbirds, suggesting that selection pressures associated with morphological traits and social systems are reflected in brain architecture.

Original languageEnglish (US)
Pages (from-to)1095-1099
Number of pages5
JournalBehavioral Neuroscience
Issue number5
StatePublished - 1999
Externally publishedYes

ASJC Scopus subject areas

  • Behavioral Neuroscience


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