Habitat selection, age-specific recruitment and reproductive success in a long-lived seabird
In: Thomson, D. L., Cooch, E. G., Conroy, M. J. (Eds.): Modeling demographic processes in marked populations, 365–392
Environmental and ecological statistics 3
Berlin [et al.], Springer (2009)
Like the majority of long-lived seabirds, black-legged kittiwakes delay recruitment (i.e. first reproduction); physiological, behavioural, and environmental factors are thought to explain such a delay, but how it may have evolved isn’t yet fully understood.
We first aim at investigating the relationship between habitat quality and age of first breeding. To address this, we used multistate mark-recapture approaches to model the transition from non-breeding to breeding status as a function of age and habitat quality. We also investigate the influence of recruitment decisions on reproductive success in the year of recruitment.
Our results provide evidence that recruitment probability is highest at intermediate ages (i.e. 5 to 6 years old). Importantly, recruitment probability was maximal in habitats (i.e. cliffs) of medium quality. This particular pattern suggests the existence of constraints. High-quality cliffs, where competition for nest-sites is harsh, may not be accessible to most recruits (i.e. the youngest). Additionally, recruits may be avoiding low productivity habitats where fitness prospects are low (i.e. strong predation on eggs).
In addition, recruitment probability was best predicted by apparent habitat quality the year preceding recruitment. The latest result suggests either that habitat selection takes place the year preceding settlement and first reproduction, or that the information available to individuals at the beginning of a season is temporally auto-correlated to past productivity.
We found that the youngest recruits (i.e. age three) experienced poor breeding performance at the beginning of their reproductive life, and that reproductive performance was higher for birds recruiting at intermediate age.
Defining groups of individuals recruiting at various ages may be a way of defining frailty classes using an observable criterion. Comparison of the performance of models accounting for observable versus unobservable frailty may help assess the relevance of “age at first breeding” as a criterion to define quality groups in the population. Development of statistical models accounting for unobserved heterogeneity in survival and breeding success in wild animal populations is only fairly recent and would require additional efforts for possible applications to mark recapture models.
Key words: black-legged kittiwakes, capture-mark-recapture, delayed recruitment, habitat selection, multistate modelling, reproductive performance.