Numerical and functional responses of breeding passerine species to mass occurrence of geometrid caterpillars in a subalpine birch forest: a 30-year study
Numerical and functional responses of breeding passerine species to mass occurrence of geometrid caterpillars in a subalpine birch forest: a 30-year study
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DOI：
10.1111/j.1474-919x.2004.00338.x
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发表时间：
2005-01-01
期刊：
影响因子：
2.1
通讯作者：
Hogstad, O
中科院分区：
文献类型：
--
作者：
Hogstad, O
北方天牛幼虫Epirrita auumnata和Operoptera brumata的密度具有周期性，每隔10年大量发生一次。Epirrita和Operoptera幼虫的大小分别为2-3厘米和1.5-2厘米，是雀形目鸟类的营养食物。为了检验这些幼虫在30年期间(1972-2001年)对雀形目鸟类群落(挪威中部布达尔的山桦林)是否有任何数量和/或功能上的影响，我估计了它们在桦树冠中的丰度(每100扫的幼虫数量)，以及雀形目鸟类群落中繁殖鸟类的密度。此外，从1972年到1998年，我监测了五种鸟类的筑巢成功情况。1972-78年，研究了数量最多的鸟类(成鸟和雏鸟)的觅食模式和它们的胃内容物(覆盖两种几何图形的种群高峰)。Epirrita的种群高峰出现在1975-76年、1985-86年和1996年，而Ophoptera的种群高峰出现在1976-77年、1986-87年和1997-98年。雀形目鸟类群落共有8种，26年有1种，14~21年有3种，1~4年有3种。只有黑脉金斑潜蝇种群在数量上对Epirrita和Operoptera的波动做出了反应。荆棘也是唯一一种平均窝卵数随年份变化的物种，这与Epirrita的密度呈正相关。柳莺、褐飞虱和红头翁的年平均筑巢成功率在大发生年份有较高的趋势，但只有芦苇种群的年平均筑巢成功率较高。海燕幼虫的丰度对任何鸟类的筑巢成功率没有影响。在埃皮里塔暴发年(1975-76)，雀类在桦树树冠上觅食的频率比之前或之后的几年更频繁。对5种成年雀形目鸟类及其雏鸟的分析表明，在1974-76年间，Epirrita是主要的食物项目。尽管1976年和1977年白桦树上出现了大量的角翅目昆虫，但只有少数幼虫在雀科动物的胃里被发现。在幼虫暴发后的第二年，没有一只雀类的种群密度增加，但杨柳莺和蓝嘴雀的密度在第二年有所增加，表明这些物种的返回率较高。这项研究表明了饮食反应的存在，也表明了对山桦林中Epirrita丰度变化的生殖反应。雀形目昆虫(除了荆棘鸟)对Epirrita的波动缺乏数量反应，这与北美北部温带落叶森林中的雀形目群落所描述的模式形成了鲜明对比，在北美，鳞翅目毛虫定期大规模爆发。
In northern Fennoscandia, the geometrid moths Epirrita autumnata and Operophtera brumata have cyclicities in density with mass occurrence at 10-year intervals. The larvae of Epirrita and Operophtera attain a size of 2-3 cm and 1.5-2 cm, respectively, and are nutritious food items for passerine birds. To examine whether these larvae have any numerical and/or functional influence on a passerine bird community (mountain birch forest in Budal, central Norway) during a 30-year period (1972-2001), I estimated their abundance (number of larvae per 100 sweeps) in the birch canopy, and the densities of breeding birds in the passerine community. In addition, from 1972 to 1998, I monitored the nesting success of five of the bird species. The foraging pattern of the most abundant bird species and their gizzard contents (adults and nestlings) were examined in 1972-78 (covering population peaks of both the geometrids). Population peaks of Epirrita occurred in 1975-76, 1985-86 and 1996, and of Operophtera in 1976-77, 1986-87 and 1997-98. The passerine community consisted of eight species that were territorial in all 30 years, one species in 26 years, three species in 14-21 years and three species in 1-4 years. Only the Brambling Fringilla montifringilla population responded numerically to the fluctuations of Epirrita and Operophtera. Brambling was also the only species whose mean clutch size varied between years, and this correlated positively with the density of Epirrita. The mean annual nesting success of Willow Warbler Phylloscopus trochilus, Bluethroat Luscinia svecica and Common Redpoll Carduelis flammea tended to be higher in years with mass outbreaks of Epirrita, but was significantly so only for Reed Bunting Emberiza schoeniclus. The abundance of Operophtera larvae showed no influence on the nesting success of any bird species. The passerines foraged more frequently in the birch canopy in the Epirrita outbreak years (1975-76) than in the years before or after. Gizzard analyses of five adult passerine species and their nestlings showed that Epirrita was the main food item in 1974-76. Even though Operophtera occurred in large numbers in birch trees in 1976 and 1977, only a few larvae were found in the gizzards of the passerines. None of the passerines showed an increase in their population density in the year following the larval outbreaks, but the densities of Willow Warbler and Bluethroat increased in the succeeding year, indicating a higher return rate for these species. The study shows the existence of a dietary response and also indicates a reproductive response to the changes in the abundance of Epirrita in mountain birch forest. The lack of numerical response in the passerines (except the Brambling) to the fluctuation in Epirrita contrasts with the pattern described for passerine communities in northern temperate deciduous forests in North America, where Lepidoptera caterpillars periodically have mass outbreaks.