Eeva T, Ryömä M, Riihimäki J
Section of Ecology, Department of Biology, University of Turku, 20014 Turku, Finland.
Oecologia. 2005 Oct;145(4):629-39. doi: 10.1007/s00442-005-0145-x. Epub 2005 Oct 13.
Insectivorous birds living in polluted areas are not only exposed to pollutants but they may also be affected by changes in their invertebrate food. The populations of many invertebrate species are affected by environmental pollution and such changes may lead to differences in the diet of insectivorous birds. We examined nestling food quality (invertebrate composition and heavy metal levels) and breeding performance of two cavity-nesting passerines, the Great tit, Parus major, and the pied flycatcher, Ficedula hypoleuca, in an area with long-term heavy metal pollution by a copper smelter. There were no differences in feeding frequencies or the amount of food that parents provided to their nestlings between polluted and unpolluted sites, but food quality in a polluted area differed from that of the control area in both bird species. P. major took more beetles and variable "flying insects" and less caterpillars (of smaller size) and moths in the polluted area as compared to the unpolluted one. F. hypoleuca ate more beetles and larvae and less moths and spiders in the polluted area. Breeding success of P. major was better when the nestling diet contained a large proportion of caterpillars and the relationship was especially strong in the polluted area. On the contrary, F. hypoleuca broods succeeded equally well with variable diets. Our data suggest that a more opportunistic forager, F. hypoleuca, is less vulnerable to a changing invertebrate composition caused by human environmental impacts than a caterpillar specialist, P. major. In a heavy metal polluted area, F. hypoleuca seems to be more sensitive to a decreased amount of Ca rich food items (e.g. snails) while P. major suffers especially from the lack of carotenoid rich caterpillars. Our results emphasize the importance of secondary environmental changes, like food quality, in addition to direct impacts of pollutants.
生活在污染地区的食虫鸟类不仅会接触到污染物，它们的无脊椎动物食物的变化也可能对其产生影响。许多无脊椎动物物种的数量受到环境污染的影响，而这种变化可能导致食虫鸟类的饮食差异。我们研究了在一个受铜冶炼厂长期重金属污染的地区，两种洞巢雀形目鸟类——大山雀（Parus major）和斑姬鹟（Ficedula hypoleuca）的雏鸟食物质量（无脊椎动物组成和重金属含量）以及繁殖表现。在污染和未污染地点之间，亲鸟给雏鸟喂食的频率或食物量没有差异，但在这两种鸟类中，污染地区的食物质量与对照地区不同。与未污染地区相比，大山雀在污染地区捕食更多甲虫和各类“飞行昆虫”，而捕食较少（体型较小的）毛虫和蛾类。斑姬鹟在污染地区吃更多甲虫和幼虫，而吃较少蛾类和蜘蛛。当雏鸟的饮食中含有很大比例的毛虫时，大山雀的繁殖成功率更高，并且在污染地区这种关系尤为明显。相反，斑姬鹟雏鸟在饮食多样的情况下繁殖成功率同样良好。我们的数据表明，与专门捕食毛虫的大山雀相比，更具机会主义觅食习性的斑姬鹟受人类环境影响导致的无脊椎动物组成变化的影响较小。在重金属污染地区，斑姬鹟似乎对富含钙的食物（如蜗牛）数量减少更为敏感，而大山雀尤其受到缺乏富含类胡萝卜素的毛虫的影响。我们的结果强调了除污染物的直接影响外，诸如食物质量等次生环境变化的重要性。
