Variation in social rank acquisition influences lifetime reproductive success in black-capped chickadees |
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Authors: | KRISTIN A SCHUBERT DANIEL J MENNILL SCOTT M RAMSAY KEN A OTTER PETER T BOAG LAURENE M RATCLIFFE |
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Institution: | Department of Biology, Queen's University, Kingston, ON, K7L 3N6, Canada; Department of Biological Sciences, 401 Sunset Avenue, Biology Building, University of Windsor, Windsor, ON, N9B 3P4, Canada; Department of Biology, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada; Ecosystem Science &Management Program, University of Northern British Columbia, 333 University Way, Prince George, BC, V2N 4Z9, Canada |
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Abstract: | Dominance relationships structure many animal societies, yet the process of rank attainment is poorly understood. We investigated acquisition of social dominance in winter flocks and its fitness consequences in male black-capped chickadees (Poecile atricapillus) over a 10-year period. Age was the best predictor of rank, and paired comparisons showed high-ranked males to be older than their low-ranked flock-mates. When controlling for age, morphological variables did not predict male social rank, but high-ranked males were heavier, had lower fat scores and were in leaner condition than low-ranked males. Males that survived between years tended to increase in rank over time; however, the rate of rank advancement varied individually. Rank reversals between familiar contestants were rare, and changes in male social rank were associated with changes in flock membership. Average lifetime reproductive success (LRS) of males and females was variable and best predicted by lifespan. Male rank history also influenced realized reproductive success. Birds with higher average rank over their lifespan were more likely to reproduce successfully. However, among successful birds, average rank did not significantly predict LRS. Thus, birds that lived longer and attained high social rank earlier had higher fitness, but this effect was not manifested as fine-scale differences among successful individuals. Taken together, these findings demonstrate the importance of social factors influencing individual fitness. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 85–95. |
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Keywords: | dominance flock fidelity individual history |
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