Division for Natural Environment, Korea Environment Institute, Sejong, 30147, Republic of Korea.
Sci Rep. 2024 Aug 22;14(1):19527. doi: 10.1038/s41598-024-70330-9.
Parents adjust their foraging effort according to the chick and their own body condition and dual foraging strategy is one of the foraging tactics parents replenish their own reserves while feeding their chicks. During the post-breeding season, seabirds disperse to recover their own body condition and prepare for the next breeding season. Recently, we discovered Black-tailed gulls (Larus crassirostris) breeding around the Korean Peninsula occasionally foraging long trips during the late fledging, however, our understanding of the behavioral patterns of Black-tailed gulls during the late fledging and post-breeding, as well as its inter-colonial differences, remains considerably limited. Here, we employed 92 GPS trackers to adult Black-tailed gulls (Larus crassirostris) from six breeding colonies around the Korean peninsula (Yellow Sea-three colonies, South Sea-one colony, and East Sea-two colonies). To determine the foraging investment during the fledging, we suggested the flight efficiency in each trip as the ratio of maximum foraging distance (i.e., straight line distance) to total foraging distance (i.e., sum of all consecutive distance for each trip). Overall, the mean flight efficiency of the long foraging trips were lower than 57% (40.76 ± 13.07%) whereas that of the short foraging trips were over 74% (80.87 ± 4.03%). This may suggest that Black-tailed gulls may visited more than one foraging site during the long foraging trip while they flew directly between the foraging site and breeding colony during the short foraging trip to invest more in their juvenile. Moreover, longer maximum foraging distance with higher flight efficiency observed in the East Sea may indicate a balance between the costs (such as energy expended during foraging or food competition near breeding sites) and the benefits (quantity and quality of food obtained). Our findings revealed the flight behavior of Black-tailed gulls during the late fledging and post breeding, across six breeding colonies, which have different competition pressures and proximity to foraging site.
父母会根据雏鸟和自身的身体状况调整觅食努力程度，而双重觅食策略是父母在喂养雏鸟的同时补充自身储备的觅食策略之一。在繁殖季节之后，海鸟会分散开来恢复自身的身体状况，为下一个繁殖季节做准备。最近，我们发现，在朝鲜半岛周围繁殖的黑尾鸥偶尔会在雏鸟后期离巢时进行长途觅食，但我们对黑尾鸥在雏鸟后期和繁殖季节后的行为模式及其在不同繁殖地之间的差异的了解仍然相当有限。在这里，我们使用 92 个 GPS 追踪器对来自朝鲜半岛六个繁殖地（黄海三个繁殖地、南海一个繁殖地和东海两个繁殖地）的 92 只成年黑尾鸥（Larus crassirostris）进行了追踪。为了确定在离巢期间的觅食投资，我们提出了每次旅行的飞行效率作为最大觅食距离（即直线距离）与总觅食距离（即每次旅行的所有连续距离之和）的比值。总体而言，长途觅食旅行的平均飞行效率低于 57%（40.76±13.07%），而短途觅食旅行的平均飞行效率则超过 74%（80.87±4.03%）。这可能表明，黑尾鸥在长途觅食旅行中可能会访问多个觅食地点，而在短途觅食旅行中，它们会直接在觅食地点和繁殖地之间飞行，从而在幼鸟身上投入更多的精力。此外，在东海观察到的最大觅食距离更长且飞行效率更高，这可能表明在成本（如觅食期间消耗的能量或繁殖地附近的食物竞争）和收益（获得的食物数量和质量）之间达到了平衡。我们的研究结果揭示了黑尾鸥在六个繁殖地的雏鸟后期和繁殖季节后的飞行行为，这些繁殖地的竞争压力和觅食地点的接近程度各不相同。
