Reproductive ageing and age-dependent parental effects on offspring in a long-lived seabird

1. The ageing rate of reproductive traits can greatly vary between individuals of a same species. Furthermore, the parental age can sometimes influence the phenotype of the next generation. 2. Although several studies have addressed ageing in wild animals, we still have a limited understanding of the ageing pattern of multiple reproductive traits in both sexes and, in particular, whether parental age influences the offspring phenotype. 3. We used a long-term longitudinal dataset of reproductive data collected from a population of a long-lived seabird, the Scopoli’s shearwater, to analyse (i) how a set of parental traits (i.e., individual reproductive success, body mass during breeding, and egg size) change with age in females and in males, and (ii) the occurrence of age-dependent parental effects on the body mass and skeletal traits of the offspring. 4. We found evidence for an age-related decline in the body mass of males and in the egg volume of females. There was no statistically significant effect of age on reproductive success. We also observed that parental age affected the body mass of the offspring but not the skeletal measures: older parents generated smaller female chicks but larger male chicks at fledging than younger parents. 5. Our study highlights that reproductive ageing is not a uniform process, but rather it varies among traits and between sexes. Moreover, our study reveals that parental age may influence differently female and male offspring, which could have potential implications for population demography.