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

Abstract

Summary1. Many studies have provided evidence that ®rst-time breeders have a lower survival, a lower probability of success, or of breeding, in the following year. Hypotheses based on reproductive costs have often been proposed to explain this. However, because of the intrinsic relationship between age and experience, the apparent inferiority of ®rst-time breeders at the population level may result from selection, and experience may not in¯uence performance within each individual. In this paper we address the question of phenotypic correlations between ®tness components. This addresses dierences in individual quality, a prerequisite for a selection process to occur. We also test the hypothesis of an in¯uence of experience on these components while taking age and reproductive success into account: two factors likely to play a key role in a selection process. 2. Using data from a long-term study on the kittiwake, we found that ®rst-time breeders have a lower probability of success, a lower survival and a lower probability of breeding in the next year than experienced breeders. However, neither experienced nor inexperienced breeders have a lower survival or a lower probability of breeding in the following year than birds that skipped a breeding opportunity. This suggests heterogeneity in quality among individuals. 3. Failed birds have a lower survival and a lower probability of breeding in the following year regardless of experience. This can be interpreted in the light of the selection hypothesis. The inferiority of inexperienced breeders may be linked to a higher proportion of lower-quality individuals in younger age classes. When age and breeding success are controlled for, there is no evidence of an in¯uence of experience on survival or future breeding probability. 4. Using data from individuals whose reproductive life lasted the same number of years, we investigated the in¯uence of experience on reproductive performance within individuals. There is no strong evidence that a process operating within individuals explains the improvement in performance observed at the population level.

Now you see him, now you don't: experience, not age, is related to reproduction in kittiwakes

“…For example, breeding probability has been shown to be associated with divorce or dispersal in several species [15,24,40]. In addition, in this study population, previous results have provided evidence that the probability of breeding in the following year differs according to previous breeding success (for birds involved in the breeding process) [19,23]. Because of the well-known relationship between breeding success, dispersal and divorce, subsequent breeding probability is likely to vary with any of these covariates, as well as with those associated with breeding success itself [15,16].…”

“…The classical explanation for this pattern is the trade-off between current and future reproduction [35,36]. Investment in current reproduction may have a cost in terms of reduced survival or future reproduction [4], and experienced breeders, having acquired abilities increasing the efficiency of their activities [19], may use less energy than inexperienced breeders to breed. Consequently, some of the inexperienced birds would skip reproduction whereas experienced kittiwakes would not in the next season.…”

“…Every year, colonies were intensively searched for banded birds from January to August, though the large majority of data come from the more restricted nesting period, mid-April to mid-August. During a breeding season, a bird may be missed (not seen) or seen either as a pre-breeder [18,19], as a breeder or as a non-breeder. An individual was considered as a breeder if its nest reached a completion criterion [20].…”

Frequent skipped spawning in the world’s largest cod population

“…Reproductive investment may vary according to factors such as territory quality and age (28)(29)(30), and similarly, the "decision" to skip spawning is likely influenced by internal physiological state. We found that developing females had larger energy reserves than nondeveloping females (Fig.…”

Neutral theory for life histories and individual variability in fitness components

“…In many studies on natural populations we lack information on individual genotypes, but many studies use the values of these individual components of fitness to infer underlying differences in genotypic fitness and thence to study evolutionary change. These studies have used diverse methods: statistical models of unobserved differences at birth (23)(24)(25); studies of the correlation among fitness components (26)(27)(28); and the use of pedigrees to determine heritability, the fraction of the variance in fitness components that is due to underlying additive genetic variation (1,2,29).…”