Forsman Jukka T, Mönkkönen Mikko, Helle Pekka, Inkeröinen Jouko
Department of Biology, University of Oulu, POB 333, FIN-90571 Oulu, Finland Fax +358-8-5531227; e-mail:
Finnish Game and Research Institute, Meltaus Game Research Station, FIN-97340 Meltaus, Finland, , , , , , FI.
Oecologia. 1998 Jun;115(1-2):278-286. doi: 10.1007/s004420050517.
We studied experimentally how heterospecific attraction may affect habitat selection of migrant passerine birds in Finnish Lapland. We manipulated the densities of resident tit species (Parus spp.). In four study plots residents were removed before the arrival of the migrants in the first study year, and in four other plots their densities were increased by releasing caught individuals. In the second year the treatments of the areas were reversed, allowing paired comparisons within each plot. We also investigated the relative abundance of arthropods in the study plots by the sweep-net method. This allowed us to estimate the effect of food resources on the abundance of birds. The heterospecific attraction hypothesis predicts that densities of migrant species (especially habitat generalists) would be higher during increased resident density. Results supported this prediction. Densities and number of the most abundant migrant species were significantly higher when resident density was increased than when they were removed. On the species level the redwing (Turdus iliacus) showed the strongest positive response to the increased abundance of tits. Migrant bird abundances seemed not to vary in parallel with relative arthropod abundance, with the exception of the pied flycatcher (Ficedula hypoleuca) which showed a strongly positive correlation with many arthropod groups. The results of the experiment indicate that migrants can use resident tit species as a cue to a profitable breeding patch. The relationship between the abundance of the birds and arthropods suggests that annual changes in food resources during the breeding season probably do not have a very important effect on bird populations in these areas. The results stress the importance of positive interspecific interactions in structuring northern breeding bird communities.
我们通过实验研究了异种吸引如何影响芬兰拉普兰地区候鸟雀形目鸟类的栖息地选择。我们操控了当地山雀物种（大山雀属）的密度。在第一个研究年度，在四个研究地块中，在候鸟抵达之前移除了当地山雀；在另外四个地块中，通过放生捕获的个体增加了它们的密度。在第二年，对这些区域的处理方式进行了反转，以便在每个地块内进行配对比较。我们还通过扫网法调查了研究地块中节肢动物的相对丰度。这使我们能够估计食物资源对鸟类数量的影响。异种吸引假说预测，在当地山雀密度增加期间，候鸟物种（尤其是栖息地泛化种）的密度会更高。结果支持了这一预测。当当地山雀密度增加时，最常见候鸟物种的密度和数量显著高于移除当地山雀时。在物种层面上，欧歌鸫（Turdus iliacus）对山雀数量增加的正向反应最为强烈。候鸟的数量似乎并未与节肢动物的相对丰度呈平行变化，但白斑姬鹟（Ficedula hypoleuca）除外，它与许多节肢动物类群呈强正相关。实验结果表明，候鸟可以将当地山雀物种作为寻找适宜繁殖地的线索。鸟类数量与节肢动物数量之间的关系表明，繁殖季节食物资源的年度变化可能对这些地区的鸟类种群没有非常重要的影响。这些结果强调了积极的种间相互作用在构建北方繁殖鸟类群落中的重要性。
