Influence of helping and breeding experience on reproductive performance in the Seychelles warbler: a translocation experiment

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Reproductive success of the cooperative breeding Seychelles warbler (Acrocephalus sechellensis) increases with age. This age effect is not due to differential survival or increased reproductive effort, but to accumulated helping and breeding experience. In their first year of breeding, reproductive performance of inexperienced warblers with neither helping nor breeding experience was significantly lower than that of warblers of the same age with either previous helping or breeding experience. Reproductive performance was the same for primiparae with helping experience and for birds with breeding experience. Female primiparae with helping experience or breeding experience built better nests and spent more time incubating than inexperienced females, which led to increased hatching success. Male primiparae with helping experience or males with breeding experience guarded the clutch better than inexperienced males, which led to reduced egg predation. Even-aged warblers with different previous experiences were transferred to unoccupied islands, where birds started breeding immediately in high-quality territories. The experiment showed that birds with helping experience produced their first fledgling as fast as experienced breeders, and significantly faster than inexperienced birds. Breeding performance did not improve further with experience after the first successful breeding attempt. Only birds with previous breeding experience who paired with inexperienced birds, were likely to change mate. The other pair combinations remained stable. Thus, primiparous birds with helping experience have greater lifetime reproductive success than inexperienced primiparae of the same age. This experiment shows that helping behavior has not only been selected for in the context of promoting an individual's indirect fitness, but also in the context of gaining helping experience which translates into improved reproductive success when a helper becomes a breeder.