Influence of breeding success on fidelity in long-lived birds: an experimental study

In long-lived birds, reproductive performance is considered to increase with breeding experience, influencing site and mate retention. However, breeding success also depends on external factors. We therefore increased experimentally the breeding success of a population of White-chinned Petrels Procellaria aequinoctialis that had been suffering from black rat Rattus predation. Thus, we were able to control for intrinsic and extrinsic factors when studying relationships between reproduction and fidelity in this long-lived and faithful species. Rat poisoning led to a significant increase of breeding success, site and mate fidelity. Breeding success increased with individual experience and breeding failure affected burrow fidelity significantly, but only during the period when rats were not poisoned. After rat poisoning had started, birds were more likely to retain their burrows as they became more experienced, but breeding success and experience had no effect on mate fidelity in either period. Although White-chinned Petrels seemed to change burrow or mate in order to improve their breeding success, the major factor causing changes was disturbance caused by rats rather than breeding failure per se. Variations in mate fidelity appeared to be merely a consequence of variation in burrow fidelity. Our results disagree with most studies on long-lived and faithful species. Therefore, controlling for both intrinsic and extrinsic factors is desirable, and comparisons within and between populations should be combined whenever possible when studying life-history traits.