Niche partitioning among different age, breeding status or sex classes allows resource use to be maximized while reducing intraspecific competition. Individual specialization marks the finest scale of niche partitioning where, within a species, individuals differ in their realized niches. Despite having important implications in ecology, evolution and conservation, studies simultaneously addressing the occurrence of both phenomena are scarce. We studied niche partitioning and individual specialization in foraging behaviour in relation to age, breeding status and sex using breeding, nonbreeding adult and immature Scopoli's shearwaters, Calonectris diomedea, in Minorca (Balearic Is.) during chick rearing in 2017 with GPS loggers and stable isotopes. Compared to adults, immature birds seemed to exploit a larger area at the population level, possibly to avoid competition. We found similar levels of individual specialization in immature and adult birds, which suggests the former have well-defined foraging strategies prior to prospecting the colony. For breeding status, we did not find niche partitioning or differences in individual specialization, suggesting nest attachment and pair bonds also lead to central-place foraging in nonbreeding adults. Male breeders showed greater individual specialization than female breeders in trip characteristics. At the same time, individual specialization in isotopic diet was higher in females than in males. These opposite patterns are possibly driven by a greater use of fishery discards by males, which would underlie their individual strategies of following vessels, resulting in a highly variable diet, since discarded prey types vary more than naturally accessible prey. Our results suggest that seabirds acquire individual strategies early in life and, once they are sexually mature, breeding constraints do not result in differences in feeding behaviour between breeders and nonbreeders. Finally, we showed that sexual differences in individual specialization can apparently emerge even in slightly dimorphic species sharing breeding duties.

中文翻译：

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长寿海鸟年龄、繁殖状态和性别等级的生态位划分和个体专业化

不同年龄、育种状态或性别类别之间的生态位划分可以最大限度地利用资源，同时减少种内竞争。个体专业化标志着生态位划分的最佳规模，在一个物种内，个体在他们实现的生态位上有所不同。尽管在生态学、进化和保护方面具有重要意义，但同时解决这两种现象发生的研究很少。我们使用 2017 年在米诺卡岛（巴利阿里群岛）养鸡期间使用 GPS 记录器和稳定同位素在米诺卡岛（巴利阿里群岛）的繁殖、非繁殖成年和未成熟的斯科波利剪刀海鸥 Calonectris diomedea 研究了与年龄、繁殖状态和性别相关的觅食行为的生态位划分和个体专业化. 与成鸟相比，未成熟的鸟类在种群水平上似乎利用了更大的区域，可能是为了避免竞争。我们在未成熟和成年鸟类中发现了相似的个体专业化水平，这表明前者在探索群体之前具有明确的觅食策略。对于繁殖状态，我们没有发现生态位划分或个体专业化的差异，这表明巢穴附着和配对也会导致非繁殖成虫在中心位置觅食。在旅行特征方面，雄性育种者比雌性育种者表现出更大的个体专业化。与此同时，女性在同位素饮食方面的个体化程度高于男性。这些相反的模式可能是由雄性更多地使用渔业丢弃物所驱动的，这将成为他们跟随船只的个人策略的基础，导致高度可变的饮食，因为丢弃的猎物类型比自然可接近的猎物变化更大。我们的研究结果表明，海鸟在生命早期就获得了个体策略，一旦它们性成熟，繁殖限制不会导致繁殖者和非繁殖者之间的进食行为存在差异。最后，我们表明，即使在分担育种职责的略微二态的物种中，个体专业化的性别差异也会明显出现。