Consequences of recruitment decisions and heterogeneity on age‐specific breeding success in a long‐lived seabird

Abstract

An individual's age at first reproduction and investment in successive reproductive attempts are involved in mechanisms that can impede somatic repair, resulting in a decline in reproductive abilities with age (reproductive senescence). We used long-term data from the Black-legged Kittiwake, a long-lived seabird, to address the relationship between recruitment age, age-specific breeding success (BS), and reproductive senescence, while accounting for breeding experience and temporal variation in BS. We first detected late-life improvement in BS across all recruitment groups, which we recognized as "within-generation selection" or the selective disappearance of "frail" phenotypes. When such heterogeneity was accurately accounted for, we showed that all individuals suffered reproductive senescence. We first highlighted how different combinations of pre- and post-recruitment experience across recruitment groups resulted in maximal BS at intermediate ages. BS increased in early recruits as they gained post-recruitment experience, whereas late recruits gained pre-recruitment experience that led to high BS at recruitment. Only individuals recruiting at intermediate ages balanced their pre- and post-recruitment experience. Consistent with the "cumulative reproductive cost hypothesis," we also observed a faster decline in BS in early recruits at advanced ages, whereas individuals delaying recruitment experienced the slowest decline in BS with age. Early recruits, however, reached the highest levels of BS at intermediate ages, sensus stricto (10-13 years old), whereas individuals delaying recruitment experienced the lowest at similar ages. These divergent trajectories may reflect a "delayed trade-off" balancing a maximization of midlife BS against reproductive senescence at advanced ages. Additionally, annual variation in BS had a greater effect on individuals early in life, suggesting that experienced individuals were able to buffer out the effects of temporal variation on BS, which can ultimately improve fitness in stochastic environments. Our findings stress that (1) both observed and unobserved heterogeneity are important in detecting within-individual senescence, and (2) short-term trade-offs may be rare in long-lived species; thus, cumulated reproductive costs should be invoked as an alternative mechanism underlying reproductive senescence.

Effects of climatic variation and reproductive trade‐offs vary by measure of reproductive effort in greater sage‐grouse

“…Individual heterogeneity in reproductive output and cost of reproduction has been shown in mammalian (Hamel et al 2009) and avian (Aubry et al 2009, Aubry et al 2011, Cam et al 2013) taxa and could be present in our system as evidenced by differential effects of previous brood success on subsequent hatch success (negative slope) and brood success (positive slope). The differential effects lead us to conclude that most individuals that produce a successful brood subsequently fail to achieve complete reproductive success in the following year (i.e., failed hatch success).…”

Reproductive improvement and senescence in a long-lived bird

“…We found only two studies that do not show any improvement in certain reproductive performance measures when accounting for compositional change, although there was an apparent improvement when not accounting for the bias. In the black-legged kittiwakes, the entire apparent improvement in breeding success (success or failure) was due to selective appearance and selective disappearance (60). The apparent improvement in egg volume for the oystercatcher in the study of van de Pol and Verhulst (5) was entirely explained by the selective appearance of individuals laying larger eggs at older ages.…”

Extreme climate events and individual heterogeneity shape life‐history traits and population dynamics

“…For example, some high-quality individuals may be more efficient foragers, have higher rates of offspring provisioning, and have a higher chance of successfully raising offspring than low-quality individuals (Lewis et al 2006, Lescroe¨l et al 2009. High-quality individuals breeding successfully in a given year may also tend to survive and reproduce with a higher probability in the following year compared to failed breeders and nonbreeders (individuals that skipped reproduction in a given year; Cam and Monnat 2000, Cam et al 2002, Aubry et al 2009. Such high-quality individuals often contribute the majority of recruits in subsequent generations, which in turn has important consequences for population dynamics and evolutionary processes (i.e., they tend to be the most fit; Aubry et al 2009).…”

“…Individual heterogeneity can vary according to factors such as age or experience gained as environmental conditions change. For example, reproductive success can increase as an individual becomes more experienced (Aubry et al 2009), while survival can be reduced at older ages by accumulated damage induced by the environment. We investigate individual heterogeneity for a seabird in both ordinary conditions and extreme favorable and unfavorable conditions.…”