Korpimäki Erkki
Department of Zoology, University of Oulu, Linnanmaa, SF-90570, Oulu, Finland.
Oecologia. 1986 May;69(2):195-201. doi: 10.1007/BF00377621.
I studied the importance of geographical location, snow cover and food to the fluctuations in 30 breeding populations of Tengmalm's owl (Aegolius funereu) in Europe. Cyclicity indices were positively related both to latitude and longitude, but within Fennoscandia they were better correlated with snow cover. Population fluctuations increased northward, while food niche breadth and degree of site tenacity decreased northwards.Microtine fluctuations become more pronounced northwards and are more synchronized, while number of alternative prey increases southwards. These factors promote instability in North European and stability in central European owl populations. Furthermore, snow conditions were more important within Fennoscandia, since this small owl cannot hunt voles protected by deep snow. Environmental predictability and diversity of available food for Tengmalm's owl increase southwards in Europe. Thus, the owl is a resident generalist predator of small mammals and birds in central Europe and adopts a partial migration strategy (males being resident and females nomadic) in South and West Finland, changing its habits to nomadic microtine specialist in areas with pronounced vole cycles (in northern Fennoscandia). These changes fit well with the recent suggestion that gradients in density variations of small rodents are related to sustainable numbers of generalist predators.
我研究了地理位置、积雪覆盖和食物对欧洲30个长尾林鸮（Aegolius funereus）繁殖种群数量波动的重要性。周期性指数与纬度和经度均呈正相关，但在芬兰斯堪的纳维亚地区，它们与积雪覆盖的相关性更好。种群数量波动向北增加，而食物生态位宽度和栖息地忠诚度向北降低。田鼠数量的波动向北变得更加明显且更加同步，而替代猎物的数量向南增加。这些因素导致北欧猫头鹰种群不稳定，而中欧猫头鹰种群稳定。此外，在芬兰斯堪的纳维亚地区，积雪条件更为重要，因为这种小型猫头鹰无法捕食被深厚积雪保护的田鼠。欧洲长尾林鸮可利用食物的环境可预测性和多样性向南增加。因此，在中欧，这种猫头鹰是小型哺乳动物和鸟类的定居性广食性捕食者，在芬兰南部和西部采取部分迁徙策略（雄性定居，雌性游牧），在田鼠数量周期明显的地区（芬兰斯堪的纳维亚北部）改变习性成为游牧性田鼠专食者。这些变化与最近的观点非常契合，即小型啮齿动物密度变化的梯度与广食性捕食者的可持续数量有关。
