Chapter Eight - The Study of Career Decisions: Oystercatchers as Social Prisoners
To understand the social organization of species, we propose that it is necessary to unify three partial descriptions of social systems based on competition for limiting resources: adaptive distribution theory, life-history theory, and mating systems theory. Here, we illustrate what insights can be gained by applying such a framework to the study of the various social positions that make up the social career of Eurasian Oystercatchers Haematopus ostralegus. During both the breeding and nonbreeding season, Oystercatchers are despotically distributed over limiting resources. We suggest that during the breeding season, nonbreeders delay reproduction by queuing for high-quality territories, and during the nonbreeding season, birds may queue for high dominance to enhance survival. The queue models potentially meet a key goal, namely, the ability to predict the mean and the variability in the age at which particular social positions are reached, as well as predicting the structure of the Oystercatcher society (i.e., the distribution of social positions) from the distribution of limiting resources. More work is needed to investigate whether the career decision where and when to start reproducing is also linked to the decision with whom to settle, or whether mate choice mainly operates after settlement via divorce. There are clear differences between the sexes in morphology, feeding specialization, and divorce strategy, but we are poorly informed on sex-specific differences in other career decisions. Furthermore, the difficulty in following individuals year-round means we still have relatively little knowledge how the career decisions in the nonbreeding and breeding seasons are linked through carry-over effects via an individual's state.
Ens B.J., Van de Pol M. & Goss-Custard J.D.