Variability in the Foraging Distribution and Diet of Cape Gannets between the Guard and Post-guard Phases of the Breeding Cycle
Variability in the Foraging Distribution and Diet of Cape Gannets between the Guard and Post-guard Phases of the Breeding Cycle
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DOI：
10.3389/fmars.2018.00015
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发表时间：
2018-02-20
影响因子：
3.7
通讯作者：
Pistorius, Pierre A.
中科院分区：
文献类型：
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作者：
Botha, Jonathan A.;Pistorius, Pierre A.
在繁殖期间，海鸟是觅食的中心，对当地猎物的变化很敏感。随着繁殖季节的进展，觅食行为和分布预计将改变当地猎物的可用性可能发生的变化。此外，成年性别和成长中的小鸡不断增加的营养需求也可能影响个体的觅食行为。目前，相对较少的研究已经评估了觅食行为的成年鸟类在后期后保卫阶段的小鸡饲养。通过GPS跟踪和饮食采样相结合，我们调查了觅食距离，空间分布和猎物组成的成年角塘鹅（桑capensis）在警卫和后警卫阶段的小鸡饲养。我们没有发现明确的证据一致的性别特异性差异觅食距离和空间分布在警卫阶段，虽然边缘差异的核心觅食区的位置在后警卫阶段是显而易见的。结果，然而，揭示了一个明显的增加觅食范围从早期的后卫到后期后卫阶段的小鸡饲养。在12月期间，饮食几乎完全由鲱鱼（Engraulis encrasicolus）组成，到1月饮食中的比例显着下降。这反映在秋刀鱼（Scomberesox saurus）的比例大幅增加。这些结果表明，角塘鹅表现出灵活性的觅食行为和饮食，这可能与猎物的丰度和分布的变化，或可能反映了不断增长的后代的能量需求的变化。本研究提供了第一次评估的角塘鹅觅食行为和空间分布在后警卫阶段的小鸡饲养。强调了在营养和海洋空间规划研究中使用海鸟跟踪数据时考虑觅食分布的年内变化的重要性。
During breeding, seabirds are central place foragers and are sensitive to changes in local prey availability. As the breeding season progresses, foraging behavior and distribution is expected to change in response to possible changes in local prey availability. In addition, adult gender, and the increasing nutritional demands of a growing chick may also influence the foraging behavior of individuals. At present, relatively few studies have assessed the foraging behavior of adult birds during the late post-guard stages of chick rearing. Through a combination of GPS tracking and diet sampling we investigated the foraging distances, spatial distribution, and prey composition of adult Cape gannets (Morus capensis) during the guard and post-guard stages of chick rearing. We found no clear evidence for consistent sex-specific differences in foraging distances and spatial distribution during the guard stage, although marginal differences in the location of core foraging areas during the post-guard stage were apparent. Results, however, revealed a clear increase in foraging range from the early guard to the late post-guard stage of chick rearing. During December the diet was comprised almost exclusively of anchovy (Engraulis encrasicolus), the proportion of which had decreased significantly in the diet by January. This was mirrored by a substantial increase in the proportion of saury (Scomberesox saurus). These results suggest that Cape gannets show flexibility in the foraging behavior and diet, which may be related to changes in the abundance and distribution of prey or may reflect changes in the energetic requirements of the growing offspring. This study provides the first assessment of Cape gannet foraging behavior and spatial distribution during the post-guard stage of chick rearing. The importance of considering intra-annual variability in foraging distribution when using seabird tracking data in trophic and marine spatial planning studies are highlighted.