The role of extra-pair mating and cooperative behaviours for the evolution of avian mating systems

Author(s): Jørgensen C, Mangel M, Eliassen S

Summary:

There is a range of bird mating systems and sex roles, from true genetic monogamy, via social monogamy with extra-pair mating, lekking, and through to group breeding. We explain this continuum from ecological factors using evolutionary simulation models with typical reproductive trade-offs. The key mechanism is that extra-pair mating may trigger male-male cooperation, because extra-pair males benefit from diverting their behavioural efforts towards the neighbourhood where they potentially have offspring rather than monopolizing it towards their domestic nest. For species with high mortality, extra-pair mating and cooperative behaviours dominate, and where extra-pair mating is very high the model’s predicted mating system resembles group breeding. For long-lived species there are two clusters of viable mating systems: lekking is predicted if females can raise the brood alone, whereas genetic monogamy is predicted where single parenting is unable to raise viable offspring, as in many seabirds. The prospect of predictively relating ecological factors to emergent breeding systems may have transferable value also for other taxa.