Predator behaviour and population numbers can be determined by many factors such as prey availability, individual and habitat characteristics, and intraspecific or interspecific factors. Using satellite telemetry, we measured home range size in 3 individuals of Red Kites (Milvus milvus) in three consecutive winters to document the pattern of spatial responses to increasing availability of its dominant prey, the Common Vole (Microtus arvalis), in the Břeclav District, Czech Republic. Starting with winter 2017/2018, we found that the home range sizes decreased in winter 2018/2019 when the index of vole population density increased from 678 burrow entrances in autumn 2017 to 1414 burrow entrances per hectare in autumn 2018. Home range sizes did not change in winter 2019/2020 in spite of the further increase in vole population density up to 6673 entrances per hectare in autumn 2019. Based on censuses at 5 communal roosts in January 2018, 2019, and 2020, we documented the pattern of numerical responses to increasing availability of voles. Numbers of wintering Red Kites did not respond to growing vole densities until they reached the highest level in autumn 2019, suggesting that the response of wintering numbers was delayed by 1 year compared to that in home range. Our study thus provides empirical support for the spatial and numerical responses of Red Kites to prey availability and suggest that these responses may differ in sensitivity to increases in vole density, being triggered at different periods of the vole population cycle.

捕食者的行为和种群数量可以由许多因素决定，例如猎物的可用性、个体和栖息地特征以及种内或种间因素。使用卫星遥测技术，我们在连续三个冬天测量了 3 只红风筝 ( Milvus milvus ) 的栖息地大小，以记录对其主要猎物——普通田鼠 ( Microtus arvalis) 的可用性增加的空间响应模式。)，位于捷克共和国 Břeclav 区。从 2017/2018 冬季开始，我们发现 2018/2019 冬季，田鼠种群密度指数从 2017 年秋季的 678 个洞穴入口增加到 2018 年秋季的每公顷 1414 个洞穴入口时，饲养范围大小有所减少。尽管 2019 年秋季田鼠种群密度进一步增加至每公顷 6673 个入口，但 2019/2020 年冬季的变化。根据 2018 年 1 月、2019 年和 2020 年 5 个公共栖息地的人口普查，我们记录了对增加田鼠的可用性。越冬红风筝的数量直到2019年秋季达到最高水平才对不断增长的田鼠密度做出反应，这表明越冬数量的响应比家庭范围延迟了1年。