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

In long-lived birds, reproductive performance is considered to increase wit h breeding experience, influencing site and mate retention. However, breedi ng success also depends on external factors. We therefore increased experim entally the breeding success of a population of White-chinned Petrels Proce llaria aequinoctialis that had been suffering from black rat Rattus predati on. 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 breed ing success, site and mate fidelity. Breeding success increased with indivi dual experience and breeding failure affected burrow fidelity significantly , but only during the period when rats were not poisoned. After rat poisoni ng had started, birds were more likely to retain their burrows as they beca me more experienced, but breeding success and experience had no effect on m ate fidelity in either period. Although White-chinned Petrels seemed to cha nge burrow or mate in order to improve their breeding success, the major fa ctor causing changes was disturbance caused by rats rather than breeding fa ilure per se. Variations in mate fidelity appeared to be merely a consequen ce of variation in burrow fidelity. Our results disagree with most studies on long-lived and faithful species. Therefore, controlling for both intrins ic and extrinsic factors is desirable, and comparisons within and between p opulations should be combined whenever possible when studying life-history traits.