Interspecific interactions within ecological networks can influence animal fitness and behaviour, including nest-site selection of birds and ants. Previous studies revealed that nesting birds and ants may benefit from cohabitation, with interspecific attraction through their nest-site choice, but mutual interactions have not yet been tested. We explored a previously undescribed ecological link between ground-nesting birds and ants raising their own broods (larvae and pupae) within the birds’ nests in a temperate primeval forest of lowland Europe. We tested whether the occurrence of ant broods within bird nests resulted from a mutual or one-sided interspecific attraction that operated through nest-site choice and was modified by weather conditions. We found a non-random occupation of bird nests by ants raising their own broods within them, which indicated interspecific attraction driven solely by the ants. The birds’ preference to nest near tussocks of vegetation showed little overlap with the most frequent placement of ant colonies among fallen deciduous tree-leaves, dead wood and moss. Additionally, birds did not appear to select forest localities with high densities of ant colonies. The occurrence of ant broods within bird nests was also unrelated to bird nest placement near to specific habitat features. The attractiveness of bird nests to ants appeared to increase with the thermal activity of the birds warming their nests, and also during cool and wet weather when the occurrence of ant broods within bird nests was most frequent. Ants often remained in the nests after the birds had vacated them, with only a slight reduction in the probability of ant brood occurrence over time. The natural patterns of bird nest colonisation by ants support the hypothesis of ants’ attraction to warm nests of birds to raise their broods under advantageous thermal conditions. Similar relationships may occur between other warm-blooded, nest-building vertebrates and nest-dwelling invertebrates, which depend on ambient temperatures. The findings advance our understanding of these poorly recognised interspecific interactions, and can inform future studies of ecological networks.

中文翻译：

---

地面筑巢鸣禽和蚂蚁之间的种间吸引力：巢穴选择的作用


生态网络内的种间相互作用可以影响动物的适应性和行为，包括鸟类和蚂蚁的巢穴选择。先前的研究表明，筑巢的鸟类和蚂蚁可能会受益于同居，通过筑巢地点的选择产生种间吸引力，但相互之间的相互作用尚未得到测试。我们探索了欧洲低地温带原始森林的地面筑巢鸟类和在鸟巢内养育自己的幼虫（幼虫和蛹）的蚂蚁之间以前未描述过的生态联系。我们测试了鸟巢内蚂蚁巢穴的出现是否是由于相互或单方面的种间吸引力造成的，这种吸引力通过巢穴选择起作用并受到天气条件的影响。我们发现蚂蚁在鸟巢中养育自己的巢穴，而不是随机占据，这表明种间吸引力完全由蚂蚁驱动。鸟类对植被草丛附近筑巢的偏好与蚁群最常见的落叶落叶、枯木和苔藓之间的分布几乎没有重叠。此外，鸟类似乎不会选择蚁群密度高的森林地区。鸟巢内蚂蚁窝的出现也与靠近特定栖息地特征的鸟巢放置无关。鸟巢对蚂蚁的吸引力似乎随着鸟类的热活动使巢穴变暖而增加，并且在凉爽和潮湿的天气下，当蚂蚁在鸟巢内筑巢时最频繁。在鸟类离开巢穴后，蚂蚁通常仍留在巢中，随着时间的推移，蚂蚁窝出现的可能性仅略有下降。 蚂蚁在鸟巢定居的自然模式支持了这样的假设：蚂蚁会被温暖的鸟巢吸引，以便在有利的热条件下养育它们的后代。其他温血筑巢脊椎动物和筑巢无脊椎动物之间也可能存在类似的关系，这取决于环境温度。这些发现增进了我们对这些鲜为人知的种间相互作用的理解，并可为未来的生态网络研究提供信息。