Understanding how invasive predators impact native species is essential for the development of effective control strategies, especially in insular environments where alternative non-native prey species exist. We examined seasonal and spatial shifts in diet of feral cat Felis silvestris catus focusing on the predation on native streaked shearwaters, Calonectris leucomelas, and introduced rats, Rattus rattus and R. norvegicus, which are alternative prey to shearwaters, on Mikura Island, Japan. Streaked shearwaters breed at low elevations on the island from spring to autumn, whereas rats inhabit the island throughout the year, which makes them an alternative prey when native shearwaters are absent. Fecal analysis revealed that feral cats dramatically shifted their diets from introduced rats in winter to streaked shearwaters in seabird-season in low elevation areas of the island, while cats preyed on rats throughout the year at high altitudes on the island. This finding suggests that feral cats selectively prey on shearwaters. This is probably because of their large body size and less cautious behavior, and because introduced rats sustain the cat population when shearwaters are absent. The number of streaked shearwaters killed was estimated to be 313 individuals per cat per year, which represents an indication of top-down effects of feral cats on streaked shearwaters. Further studies on the demographic parameters and interspecific interactions of the three species are required to enable effective cat management for the conservation of streaked shearwaters on this island.

了解侵入性捕食者如何影响本地物种对于制定有效的控制策略至关重要，尤其是在存在替代性非本地猎物物种的岛屿环境中。我们研究在野生猫的饮食季节和空间变化猫silvestris猫注重对本地大水薙鸟，捕食Calonectris leucomelas，并介绍了鼠，黑家鼠和褐家鼠在日本三浦岛上，它们是剪力水的替代猎物。从春季到秋季，斑纹的剪力水在岛上的低海拔繁殖，而整年中老鼠都栖息在岛上，这使得它们在缺乏天然剪水的情况下成为另一种猎物。粪便分析显示，野猫在冬季低海拔地区的饮食结构从冬天引入的老鼠急剧转移到海鸟季节的斑纹剪力水中，而猫则全年在岛上的高海拔地区捕食老鼠。这一发现表明，野猫选择性地捕食剪切水。这可能是因为它们较大的体型和较少的谨慎行为，并且是由于缺少切水时引入的大鼠维持了猫的种群。据估计，每条猫每年被杀死的条纹剪水数量为313个人，这表明野生猫对条纹剪水的自上而下的影响。需要对这三个物种的人口统计学参数和种间相互作用进行进一步研究，以实现有效的猫管理，以保护该岛上的斑纹剪枝水。