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.