Improvement in chick provisioning with parental experience in a seabird

Abstract

Age-related differences in the reproductive success of birds may be the result of experience-dependent changes in foraging and parental skills. We tested this hypothesis in a long-lived seabird, the common tern, Sterna hirundo. Transponder-marked birds were observed while feeding their young (1) as first-time breeders (recruits) and (2) as experienced breeders in 2 consecutive years in a breeding colony at Port Wilhelmshaven, Lower Saxony, Germany. The influence of individual breeding experience on feeding rate, feeding success and food composition was investigated, including potential year effects, using multivariate statistics. In addition, we compared the breeding success of experienced and inexperienced breeders. Feeding rate was not linked to experience, whereas experienced breeders had a higher feeding success than recruits. Both experienced breeders and recruits fed their young with the same prey species, but in recruits the proportion of prey items with low energy content was higher. The latter was linked to a lower breeding success of recruits. Our study is, to our knowledge, the first to document an individual improvement in breeding performance as a reason for age-dependent improvement in reproductive success in birds after recruitment.