Ardea
Official journal of the Netherlands Ornithologists' Union

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Caldow R.W.G. & Goss-Custard J.D. (1996) Temporal variation in the social rank of adult Oystercatchers Haematopus ostralegus. ARDEA 84 (A): 389-399
The success in interactions with conspecifics (the dominance score) of eleven out of 26 adult Oystercatchers changed significantly over several years. Since dominance score predicts dominance within dyads and hence rank within a linear hierarchy, these results suggest that hierarchies which are stable within one winter, change over longer periods. This was verified by a group of eight individuals of which six showed contested reversals of rank over four years. On the basis of external measurements it appears that individuals which increased in status and achieved high social rank were predominantly male. Comparison of the dominance scores of 'residents' and 'movers' were contrary to predictions generated by the idea that an individual's rank is determined largely by passive means as a result of the cumulative effect of prior residence. However, several comparisons were in the direction expected by this hypothesis. The relative importance of passive and active processes in determining an individual Oystercatcher's social rank remains to be evaluated. Empirical relationships indicated that changes in dominance score resulted in changes in intake rate of between -10% and +12%. Whether this effect of social rank influences fitness remains to be determined.


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