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Tests of association between the humoral immune response of red-winged blackbirds (Agelaius phoeniceus) and male plumage, testosterone, or reproductive success

  • D F Westneat
  • Dennis Hasselquist
  • J C Wingfield
Publishing year: 2003
Language: English
Pages: 315-323
Publication/Series: Behavioral Ecology and Sociobiology
Volume: 53
Issue: 5
Document type: Journal article
Publisher: Springer

Abstract english

We explored the potential relationships between male traits, reproductive success, testosterone levels in the breeding season, and Immoral immunocompetence in male red-winged blackbirds (Agelaius phoeniceus). Males responded to a single injection of diphtheriatetanus vaccine by producing antibodies to both antigens. The primary responses to each antigen were positively correlated with each other, but the relationship was clearly non-linear. No male responded strongly to diphtheria without also responding strongly to tetanus, but many males had strong responses to tetanus and weak responses to diphtheria. Response to tetanus was positively associated with hormone levels, whereas the relationship between testosterone and the response to diphtheria was weakly and nonsignificantly negative. We found no convincing relationships between immune responses and male morphological traits (epaulet size, body blackness, and body size), male success in male-male competition (territory size and tenure), or male reproductive success (number of mates, average clutch size, proportion of offspring sired, or proportion of young fledged). These results do not support testosterone acting as a constraint on immunity. Testosterone could be mediating a condition-dependent trade-off between sexual ornaments and the immune system, but the evidence for this was weak, as neither any male sexual trait nor any measure of performance was associated with immune responses. We could not eliminate the possibility that male sexual traits advertise other aspects of immunity that are not dependent upon condition or hormones.


  • Biological Sciences


  • Molecular Ecology and Evolution Lab
  • ISSN: 1432-0762
Dennis Hasselquist
E-mail: dennis [dot] hasselquist [at] biol [dot] lu [dot] se



+46 46 222 37 08



Research group


Doctoral students and postdocs

Research fellows


Jacob Roved

PhD Students, main supervisor

PhD Students, assistant supervisor


Interview about my research in the Swedish podcast "Forskarn & jag"