Apparent inferiority of first-time breeders in the kittiwake: the role of heterogeneity among age classes

1. Many studies have provided evidence that first-time breeders have a lowe r survival, a lower probability of success, or of breeding, in the followin g year. Hypotheses based on reproductive costs have often been proposed to explain this. However, because of the intrinsic relationship between age an d experience, the apparent inferiority of first-time breeders at the popula tion level may result from selection, and experience may not influence perf ormance within each individual. In this paper we address the question of ph enotypic correlations between fitness components. This addresses difference s in individual quality, a prerequisite for a selection process to occur. W e also test the hypothesis of an influence of experience on these component s while taking age and reproductive success into account: two factors likel y to play a key role in a selection process. 2. Using data from a long-term study on the kittiwake, we found that first- time breeders have a lower probability of success, a lower survival and a l ower probability of breeding in the next year than experienced breeders. Ho wever, neither experienced nor inexperienced breeders have a lower survival or a lower probability of breeding in the following year than birds that s kipped a breeding opportunity. This suggests heterogeneity in quality among individuals. 3. Failed birds have a lower survival and a lower probability of breeding i n the following year regardless of experience. This can be interpreted in t he light of the selection hypothesis. The inferiority of inexperienced bree ders may be linked to a higher proportion of lower-quality individuals in y ounger age classes. When age and breeding success are controlled for, there is no evidence of an influence of experience on survival or future breedin g probability. 4. Using data from individuals whose reproductive life lasted the same numb er of years, we investigated the influence of experience on reproductive pe rformance within individuals. There is no strong evidence that a process op erating within individuals explains the improvement in performance observed at the population level.