Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS-Université de Montpellier-Université Paul-Valéry Montpellier-EPHE, Montpellier, France.
Percy Fitzpatrick Institute of African Ornithology, NRF-DST Centre of Excellence at the University of Cape Town, Rondebosch, South Africa.
PLoS One. 2019 Feb 6;14(2):e0210328. doi: 10.1371/journal.pone.0210328. eCollection 2019.
Fisheries compete with seabirds for vanishing marine resources, but also produce fishery waste consumed by seabirds. Marine birds may therefore avoid or seek fishing vessels, and have evolved complex, plastic behavioural responses to vessel presence. Understanding these responses is essential to the conservation of a globally declining seabird community. We studied Cape gannets (Morus capensis), which compete with fisheries for reduced sardine (Sardinops sagax) resources in the Benguela upwelling region off South Africa. Using bird-borne GPS trackers coupled with newly-developed ship-radar detectors we show that foraging gannets seldom attended fishing vessels. Rather, they switched from eating scarce sardines or energetically-poor fishery waste to targeting locally abundant saury (Scomberesox saurus). This pelagic fish is brought into the seascape by warm water influx, and is not commercially exploited by fisheries. Cape gannets thereby show dietary plasticity, allowing them to maintain adult body condition and chick growth rates. This diet switch is a strong indicator that Cape gannets forage in an ecologically perturbed marine environment.
渔业与海鸟争夺日益减少的海洋资源，但也产生了海鸟可食用的渔业废物。因此，海鸟可能会避开或靠近渔船，并进化出复杂的、可塑的行为反应来应对船只的存在。了解这些反应对保护全球海鸟数量下降的社区至关重要。我们研究了南非本格拉上升流区的南非塘鹅（Morus capensis），它们与渔业争夺减少的沙丁鱼（Sardinops sagax）资源。我们使用搭载在鸟类身上的 GPS 跟踪器和新开发的船舶雷达探测器，表明觅食的塘鹅很少靠近渔船。相反，它们从吃稀有的沙丁鱼或能量低的渔业废物，转变为以当地丰富的秋刀鱼（Scomberesox saurus）为目标。这种洄游鱼类因温水流入而进入海洋景观，并不被渔业开发利用。南非塘鹅因此表现出饮食的可塑性，使它们能够维持成鸟的身体状况和雏鸟的生长速度。这种饮食的转变强烈表明南非塘鹅在生态受到干扰的海洋环境中觅食。
