Data from: Age-related variation in non-breeding foraging behaviour and carry-over effects on fitness in an extremely long-lived bird

1. Senescence has been widely documented in wild vertebrate populations, yet the proximate drivers of age-related declines in breeding success, including allocation trade-offs and links with foraging performance, are poorly understood. For long-lived, migratory species, the non-breeding period represents a critical time for investment in self-maintenance and restoration of body condition, which in many species is linked to fitness. However, the relationships between age, non-breeding foraging behaviour and fitness remain largely unexplored. 2. We performed a cross-sectional study, investigating age-related variation in the foraging activity, distribution and diet of an extremely long-lived seabird, the wandering albatross Diomedea exulans during the non-breeding period, and its links with subsequent reproductive performance. 3. We tracked the distributions of 82 adults aged 8 – 33 years with geolocator-immersion loggers and found an age-related decline in the number of landings (a proxy of foraging effort) during daylight hours. There was a decrease in body feather δ13C values in older males but not females, yet this did not accompany an age-related shift in distributions. Males conducted fewer landings than females, and the sexes were spatially segregated, with males foraging further south, likely due to their differential utilization of winds. 4. While younger (< 20 years) birds had higher foraging activity, all individuals went on to breed successfully the following season. In contrast, among older (20+ years) birds, individuals that landed more often were more likely to defer breeding or fail during incubation, suggesting they have lower foraging success. 5. As far as we are aware, this is the first demonstration of an age-specific carry-over effect of foraging behaviour in the non-breeding period on subsequent reproductive performance. This link between foraging behaviour and fitness in late but not early adulthood indicates that the ability of individuals to forage efficiently outside the breeding period may be an important driver of fitness differences in old age.

1. 野生脊椎动物种群的衰老现象已被广泛记录，但繁殖成功率随年龄下降的近因驱动因素——包括资源分配权衡及与觅食表现的关联——仍鲜为人知。对于长寿洄游物种而言，非繁殖期是投入资源进行自我维持、恢复身体状况的关键阶段，而身体状况在诸多物种中与进化适合度直接相关。然而，年龄、非繁殖期觅食行为与适合度三者之间的关联，迄今仍未得到充分探索。
2. 本研究针对一种超长寿命海鸟——漂泊信天翁（Diomedea exulans），开展了一项横断面研究，旨在探究其非繁殖期的觅食活动、分布范围与饮食的年龄相关变异，及其与后续繁殖性能的关联。
3. 研究团队通过地理定位浸没式记录仪（geolocator-immersion loggers），追踪了82只年龄介于8至33岁的成年个体的分布情况，发现日间着陆次数（可作为觅食努力的替代指标）随年龄增长而下降。老年雄性的体羽碳同位素δ¹³C值显著降低，但雌性未出现该现象，不过这一变化并未伴随分布范围的年龄相关偏移。雄性的着陆次数少于雌性，且两性存在空间隔离：雄性觅食区域更偏南，这可能与其对风力的差异化利用有关。
4. 尽管年轻个体（<20岁）的觅食活动更强，但所有个体在次年繁殖季均成功繁殖。与之形成对比的是，在年长个体（20岁以上）中，着陆次数更多的个体更有可能推迟繁殖或在孵卵阶段失败，这表明它们的觅食成功率更低。
5. 据我们所知，本研究首次证实了非繁殖期觅食行为的年龄特异性携带效应（carry-over effect）会影响后续繁殖性能。觅食行为与适合度之间的关联仅在成年后期（而非早期成年阶段）显现，这说明个体在非繁殖期高效觅食的能力，或许是老年个体间适合度差异的重要驱动因素。