Long-term fitness effects of the early-life environment in a wild bird population

Environmental conditions and experiences during development can have long-term fitness consequences, including a reduction of adulthood survival and reproduction. These long-term fitness consequences may play an important role in shaping the evolution of life history. We tested two hypotheses on the long-term fitness effects of the developmental environment—the silver spoon hypothesis and the internal predictive adaptive response (PAR) hypothesis. We compared the change in annual survival and annual reproductive output with age for adult birds hatched and/or reared in poor––impacted by anthropogenic noise, and/or high sibling competition––and good––not impacted by anthropogenic noise, and/or low sibling competition––environments. We used a 23-year longitudinal dataset from a wild house sparrow (Passer domesticus) population inhabiting an isolated island, which enabled near-complete monitoring and unusually accurate lifetime fitness estimates. We used a cross-fostering setup to disentangle environmental effects experienced postnatally from those experienced prenatally. We found that adults that, as chicks experienced more within-brood competition had a stronger increase in early-life annual survival, but also a stronger decrease in late-life annual survival. Females that hatched in a noisy environment produced fewer genetic recruits annually, supporting a sex-specific silver spoon hypothesis. Males reared in a noisy environment had accelerated reproductive schedules, supporting a sex-specific internal PAR hypothesis. Our results highlight that anthropogenic noise (∼68 dB from power generators) can have long-term fitness consequences in wild animals, altering their life-history strategies, and that effects may be sex-specific.