Behavioral Ecology and Sociobiology

, Volume 11, Issue 1, pp 13–17 | Cite as

Aggression in female Red-Winged Blackbirds: A strategy to ensure male parental investment

  • K. Yasukawa
  • W. A. Searcy


Female Red-winged Blackbirds (Agelaius phoeniceus) are often aggressive towards conspecific females during the breeding season. We hypothesize that the function of female-female aggression in this species is to guard the nonshareable portion of the male's parental investment.

The investment-guarding hypothesis predicts that a female should be more aggressive toward another female evincing interest in mating with the territory-owning male than toward a female simply perching within the male's territory. Results of mount presentations to females with active nests confirmed this prediction. Nesting females attacked a stuffed conspecific female mounted in a precopulatory, ‘soliciting’ posture significantly more often than a mount in a normal, perched posture.

The male's nonshereable parental care consists of provisioning his young, and most of this care is invested in the brood of his primary (first-to-nest) female. It is therefore predicted that primary females should be more aggressive than secondary (later-nesting) females. Female mount presentations also confirmed this prediction. Primary females attacked the soliciting mount significantly more often than secondary females.


Breeding Season Parental Care Parental Investment Active Nest Conspecific Female 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag 1982

Authors and Affiliations

  • K. Yasukawa
    • 1
  • W. A. Searcy
    • 1
  1. 1.The Rockefeller University Field Research CenterMillbrookUSA

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