Fighting ability and motivation: determinants of dominance and contest strategies in females of a passerine bird

Leslie M. Jonart, Geoffrey E. Hill, Alexander V. Badyaev

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56 Scopus citations


The communication of aggressive motivation or fighting ability has important fitness consequences for competing animals. Selection should favour rapid and honest communication between opponents to settle dominance relationships while avoiding prolonged and intense fighting. We investigated factors that influence fighting strategies and contest outcomes in female house finches, Carpodacus mexicanus, specifically focusing on the following questions. (1) What social contexts trigger an aggressive response? (2) Does body size and condition contribute to female fighting ability? (3) Do contextual factors, such as mate presence, nest status, nest proximity, and site experience contribute to fighting motivation? (4) Does contest intensity and duration increase as the differences in fighting ability between opponents decrease? (5) What is the relative contribution of fighting ability and aggressive motivation to the outcome of a contest? We found that aggression was triggered most frequently by female intrusions in the vicinity of nest and by extrapair female intrusions on an established pair. Female fighting and contest outcomes were strongly influenced by body condition and body size, and females were more motivated to initiate fights and won more contests when their mates were present. Females at the later breeding stages and those fighting closer to their nests were dominant and won more fights compared to females at earlier breeding stages or further from their nests. Females initiated a greater proportion of contests against opponents with similar local familiarity and breeding history. Escalated and prolonged contests, while rare, occurred exclusively between females of the most similar body size and condition. When differences in body condition between opponents are not easily perceived, contestants might escalate contests for more reliable assessments of relative fighting ability. Finally, body condition was not a strong determinant of contest outcome in the contexts with easily assessed differences in the resource value (e.g. mate presence), but without these motivational differences, body condition was the ultimate determinant of contest outcomes.

Original languageEnglish (US)
Pages (from-to)1675-1681
Number of pages7
JournalAnimal Behaviour
Issue number6
StatePublished - Dec 2007

Bibliographical note

Funding Information:
We thank many field assistants for help in the field, Lloyd Kiff, Daniel T. Blumstein and two anonymous referees for comments and suggestions. We are grateful to Robert McCue and the personnel of the Vigilante Ministorage for allowing us to work on their property for the last 13 years. This research was supported, in part, by US National Science Foundation (DEB-0075388, IBN-0218313, DEB-0077804) grants to A.V.B. Animal use was approved by the Auburn University Institutional Animal Care and Use Committee (PRN no. 0308-R-2463).


  • Carpodacus mexicanus
  • aggression
  • communication
  • house finch
  • passerines
  • resource holding potential


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