The impact of helping experience on helper life-history and fitness in a cooperatively breeding bird.

Cooperative breeding occurs when helpers provide alloparental care to the offspring of a breeding pair. One hypothesis of why helping occurs is that helpers gain valuable skills that may increase their own future reproductive success. However, research typically focuses on the effect of helping on short-term measures of reproductive success. Fewer studies have considered how helping affects long-term fitness measures. Here, we analyse how helping experience affects key breeding and fitness-related parameters in the Seychelles warbler (Acrocephalus sechellensis). Importantly, we control for females that have co-bred (reproduced as a subordinate by laying an egg within a territory in which they are not a dominant breeder), as they already have experience with direct reproduction. Helping experience had no significant association with any of the metrics considered, except that helpers had an older age at first dominance. Accounting for helping experience, females that had co-bred produced more adult offspring (≥1 year) after acquiring dominance and had a higher lifetime reproductive success than females that had never co-bred. Our results suggest that, in the Seychelles warbler, helping experience alone does not increase the fitness of helpers in any of the metrics considered, and highlights the importance of separating the effects of helping from co-breeding. Our findings also emphasise the importance of analysing the effect of helping at various life-history stages, as higher short-term fitness may not translate to an overall increase in lifetime reproductive success.