1. Many seabirds dive to forage, and the ability to use this hunting technique varies according to such factors as morphology, physiology, prey availability, and ambient light levels. Proficient divers are more able to seize sinking baits deployed by longline fishing vessels and may return them to the surface, increasing exposure of other species. Hence, diving ability has major implications for mitigating incidental mortality (bycatch) in fisheries.
2. Here, the diving behaviour and activity patterns of the most bycaught seabird species worldwide, the white-chinned petrel (Procellaria aequinoctialis), tracked from Bird Island (South Georgia), are analysed. Three data sources (dives, spatial movements, and immersion events) are combined to examine diverse aspects of at-sea foraging behaviour, and their implications for alternative approaches to bycatch mitigation are considered.
3. The tracked white-chinned petrels (n = 14) mostly performed shallow dives (<3 m deep) of very short duration (<5 s), predominantly during darkness, but only 7 and 10% of landings in daylight and darkness, respectively, involved diving, suggesting that surface-seizing is the preferred foraging technique. Nonetheless, individuals were able to dive to considerable depth (max = 14.5 m) and at speed (max = 2.0 m·s⁻¹), underlining the importance of using heavy line-weighting to maximize hook sink rates, and bird-scaring lines (Tori lines) that extend for long distances behind vessels to protect hooks until beyond diving depths.

中文翻译：

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白颏海燕的运动和潜水行为：昼夜变化及其对减少兼捕的影响

1. 许多海鸟潜水觅食，使用这种狩猎技术的能力因形态、生理、猎物可用性和环境光线水平等因素而异。熟练的潜水员更有能力抓住延绳钓渔船部署的下沉诱饵，并可能将它们放回水面，从而增加其他物种的暴露。因此，潜水能力对于减少渔业中的意外死亡（兼捕）具有重要意义。
2. 在这里，分析了从鸟岛（南乔治亚岛）追踪到的世界上被误捕最多的海鸟物种白颏海燕（Procellaria aequinoctialis）的潜水行为和活动模式。结合三个数据源（潜水、空间运动和浸入事件）来检查海上觅食行为的各个方面，并考虑它们对减少兼捕的替代方法的影响。
3. 被跟踪的白颏海燕 ( n = 14) 主要进行持续时间很短 (<5 s) 的浅潜水 (<3 m 深)，主要是在黑暗中，但只有 7% 和 10% 在白天和黑暗中着陆，涉及潜水，这表明表面捕获是首选的觅食技术。尽管如此，个人能够潜入相当大的深度（最大 = 14.5 m）和速度（最大 = 2.0 m·s ^-1），强调了使用重线加权来最大化鱼钩下沉率和鸟类惊吓线的重要性（托里线）在船只后面长距离延伸以保护钩子直到超出潜水深度。