Stochasticity in food availability influences vital rates such as survival and fertility. Life-history theory predicts that in long-lived organisms, survival should be buffered against environmental stochasticity showing little temporal variability. Furthermore, to optimize survival prospects, many animal species perform migrations to wintering areas where food availability is larger. Species with large latitudinal distribution ranges may show populations that migrate and others that are resident, and they may co-occur in winter. One example of these species is the predatory raptor buzzard Buteo buteo. Here, we test whether temporal variability in the density of five small mammal species of prey inhabiting different habitats (shrubland and forests) influences local annual survival of buzzards in a wintering area depending on their age and residency status (residents versus wintering individuals). We found that prey density explained a considerable amount of annual changes in local survival, which was higher for older and resident birds. This difference in local survival likely corresponded to philopatry to the wintering area, which was larger for residents and increased when prey density was larger. The total density of prey inhabiting open shrublands was the variable explaining more variance in temporal variability of local survival, even though the study area is mostly occupied by woodlands. Temporal population dynamics of the different small mammals inhabiting shrublands were not synchronous, which suggests that buzzards preyed opportunistically on the most abundant prey each winter. Generalist predation may buffer the impact of resource unpredictability for pulsed and asynchronous prey dynamics, typical of small mammals in winter.

食物供应的随机性会影响生存率和生育率等生命率。生命史理论预测，在长寿的生物体中，生存应该受到环境随机性的缓冲，环境随机性几乎没有时间变化。此外，为了优化生存前景，许多动物物种迁移到食物供应量更大的越冬地区。具有大纬度分布范围的物种可能显示迁移的种群和其他常驻种群，并且它们可能在冬季同时出现。这些物种的一个例子是掠食性猛禽秃鹰Buteo buteo. 在这里，我们测试居住在不同栖息地（灌木地和森林）的五种小型哺乳动物猎物密度的时间变化是否会影响越冬地区秃鹰的当地年度生存率，具体取决于它们的年龄和居住状态（居民与越冬个体）。我们发现猎物密度解释了当地生存率的相当大的年度变化，对于年长的和常驻的鸟类来说，这种变化更高。当地生存的这种差异可能与越冬区的捕捞活动相对应，这对居民来说更大，并且随着猎物密度的增加而增加。尽管研究区域大部分被林地占据，但栖息在开阔灌木丛中的猎物的总密度是解释当地生存时间变异性更大差异的变量。居住在灌木丛中的不同小型哺乳动物的时间种群动态并不同步，这表明秃鹰每年冬天都会机会主义地捕食最丰富的猎物。通才捕食可以缓冲资源不可预测性对脉冲和异步猎物动态的影响，这是冬季小型哺乳动物的典型特征。