Behavioral Ecology and Sociobiology

, Volume 45, Issue 3, pp 167–175

Is avian humoral immunocompetence suppressed by testosterone?


  • Dennis Hasselquist
    • Section of Neurobiology and Behavior, Cornell University Seeley G. Mudd Hall, Ithaca, NY 14853-2702, USA
  • James A. Marsh
    • Department of Immunology and Microbiology Cornell University, Veterinary Medicine Center, Ithaca NY 14853-2702, USA
  • Paul W. Sherman
    • Section of Neurobiology and Behavior, Cornell University Seeley G. Mudd Hall, Ithaca, NY 14853-2702, USA
  • John C. Wingfield
    • Department of Zoology, University of Washington, Seattle WA 98195, USA

DOI: 10.1007/s002650050550

Cite this article as:
Hasselquist, D., Marsh, J., Sherman, P. et al. Behav Ecol Sociobiol (1999) 45: 167. doi:10.1007/s002650050550


A key issue in sexual selection theory is how a correlation between male secondary sexual characters and male genetic quality can be maintained. The immunocompetence-handicap hypothesis proposes that testosterone-dependent male characters remain honest signals because of the immunosuppressive effect of elevated steroid hormone levels. The hypothesis requires that physiological levels of testosterone depress immune system function. We quantified testosterone titers and humoral immunocompetence of captive male and female red-winged blackbirds (Agelaius phoeniceus) at three points in the annual cycle (autumn, prebreeding, and breeding). We also conducted an implant experiment on the males to assess the effects of prolonged, above-normal testosterone titers on humoral immune responses. Humoral immunocompetence was measured as secondary antibody production to a non-pathogenic protein antigen, keyhole limpet hemocyanin, using an enzyme-linked immunosorbent assay we developed for A. phoeniceus. Secondary antibody responses of individuals were highly repeatable between sampling periods. Neither physiological nor above-normal levels of plasma testosterone suppressed secondary antibody production. In paired tests of the same individuals between prebreeding and breeding, and between breeding and implant, plasma testosterone increased significantly but secondary antibody responses were unaffected. We are confident in these results because with 80% power, an 11–14% difference in antibody titers would have been detected. There was no relationship between plasma testosterone levels and humoral immunocompetence in free-ranging males tested at the peak of breeding. These results cast doubt on a key assumption of the immunocompetence-handicap hypothesis.

Key words ImmunocompetenceTestosteroneImmunosuppressionSexual selectionRed-winged blackbirdELISA
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© Springer-Verlag Berlin Heidelberg 1999