Sporadic large outbreaks of herbivorous insects alter forest ecosystems via a top-down effect, and a high frequency of outbreaks led to the death of the trees on which the insects fed. The top-down effect of predators, such as other insects and birds, often regulates the outbreaks. Predator insects exert effective top-down control on outbreaks of herbivorous insects, but the effect of bird predation varies because birds have a broader diet range and higher mobility than insects. It was hypothesized that when large insect outbreaks occur during the breeding season of birds, most bird species would not respond owing to a fixed home range during this season and would, therefore, not exert top-down effects. To test this hypothesis, the relationship between bird and beech sawfly abundance was investigated for over nine years in the Tanzawa Mountains of central Japan, where temperate beech forests and large sporadic outbreaks of woody herbivorous insects occur. In this study, 28 649 female beech sawfly adults were captured, and 2515 individuals were identified from 50 bird species. The abundance of most bird species foraging on beech sawfly larvae, except , did not increase proportionally with the number of beech sawfly adults. Many bird species did not respond to the unpredictable and temporary abundance of food resources in a way that would enhance their density, supporting the hypothesis. These results can be explained by examining the nesting and foraging guilds of the birds. . is less restricted in nesting sites and nests earlier in the season than other species; therefore, they could select nests in areas where beech sawfly larvae were abundant. Regarding foraging, . has a unique foot shape that allows it to move down the tree trunk freely and respond rapidly to fluctuations in beech sawfly abundance. Bird species that exert top-down effects on insects show promise for use in an integrated pest management approach to manage sporadic outbreaks of herbivorous insects in forest ecosystems.

中文翻译：

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日本温带山毛榉林鸟类群落对木本草食性昆虫零星爆发的反应

草食性昆虫的零星大规模爆发通过自上而下的效应改变了森林生态系统，而高频率的爆发导致昆虫赖以生存的树木死亡。其他昆虫和鸟类等捕食者的自上而下的影响往往会调节疫情的爆发。捕食性昆虫对草食性昆虫的爆发发挥有效的自上而下的控制作用，但鸟类捕食的效果各不相同，因为鸟类比昆虫具有更广泛的饮食范围和更高的流动性。据推测，当鸟类繁殖季节发生大规模昆虫爆发时，由于该季节固定的活动范围，大多数鸟类不会做出反应，因此不会发挥自上而下的效应。为了验证这一假设，在日本中部的丹泽山脉对鸟类和山毛榉锯蝇丰度之间的关系进行了九年多的调查，那里有温带山毛榉森林和木本食草昆虫的大规模零星爆发。在这项研究中，捕获了 28 649 只雌性山毛榉锯蝇成虫，并从 50 种鸟类中鉴定出 2515 只个体。除 外，大多数以山毛榉叶蜂幼虫为食的鸟类的丰度并不与山毛榉叶蜂成虫的数量成比例增加。许多鸟类对不可预测的、暂时丰富的食物资源的反应并没有增加它们的密度，这支持了这一假设。这些结果可以通过检查鸟类的筑巢和觅食群体来解释。 。与其他物种相比，筑巢地点的限制较少，并且筑巢时间较早；因此，它们可以选择在山毛榉锯蝇幼虫丰富的地区筑巢。关于觅食，.具有独特的足部形状，使其能够沿着树干自由移动，并对山毛榉锯蝇丰度的波动做出快速反应。对昆虫产生自上而下影响的鸟类有望用于综合害虫管理方法，以管理森林生态系统中草食性昆虫的零星爆发。