Immunosenescence in the wild? A longitudinal study in a long‐lived seabird

1. Longitudinal studies of various vertebrate populations have demonstrated senescent declines in reproductive performance and survival probability to be almost ubiquitous. Longitudinal studies of potential underlying proximate mechanisms, however, are still scarce. 
2. Due to its critical function in the maintenance of health and viability, the immune system is among the potential (mediators of) proximate mechanisms that could underlie senescence. 
3. Here, we studied three innate immune parameters - hemagglutination titre, haemolysis titre and haptoglobin concentration - in a population of common terns (Sterna hirundo) known to undergo actuarial senescence. We repeatedly sampled birds of known sex and age across 11 years and used random regression models to (i) quantify how immune parameters vary among individuals, and (ii) describe within-individual age-specific changes in, and potential trade-offs between, immune parameters.
4. Our models revealed no differences between males and...