Data from: Interspecific social information use in habitat selection decisions among migrant songbirds

The presence of conspecifics is a social cue frequently used by songbirds in breeding-site selection. In migratory species, conspecific attraction is not possible for individuals that arrive first to breeding grounds, but these individuals may use information from ecologically similar heterospecifics. Resident tits (Paridae) are known to provide cues for migratory songbirds, however, the relevance of resident settlement decisions decreases as the season progresses. We investigated heterospecific attraction within migrant songbirds, and examined whether later arriving species use the presence of earlier arriving species as a cue for breeding habitat selection. We used a song playback experiment to test if wood warbler Phylloscopus sibilatrix settlement decisions are affected by chiffchaff Phylloscopus collybita and blackcap Sylvia atricapilla cues. Our results suggest that wood warblers used cues from heterospecifics when deciding where to breed. Wood warblers settled earlier and more numerously on plots with simulated presence of chiffchaffs, in contrast blackcap presence had a negative effect on settlement, suggesting heterospecific avoidance. Chiffchaffs and blackcaps were attracted to sites with simulated presence of conspecifics, which provides evidence for conspecific attraction in breeding-site selection of these species. Our experiment suggests that heterospecific attraction is not a phenomenon limited to resident-migrant interactions, but acts also between migrant species. Our results show an interplay of attraction and avoidance when using social cues for habitat selection decisions within a migrant songbird guild, and stress the importance of both positive and negative effects of social environment on settlement behavior of individuals.

同种个体（conspecific）的存在是鸣禽（songbirds）在进行繁殖位点选择（breeding-site selection）时频繁利用的一类社会线索。对于迁徙物种（migratory species）而言，最先抵达繁殖地的个体无法借助同种吸引策略，但可利用生态相似的异种个体（heterospecific）传递的信息。已知居留山雀（Paridae）能够为迁徙鸣禽提供相关线索，但随着季节推进，居留物种的定居决策所具备的参考价值会逐步降低。本研究针对迁徙鸣禽类群内的异种吸引现象展开探究，检验较晚抵达的迁徙物种是否会将更早到达物种的存在，作为繁殖栖息地选择的线索。我们通过鸣声回放实验（song playback experiment），检验林柳莺（Phylloscopus sibilatrix）的定居决策是否会受到叽喳柳莺（Phylloscopus collybita）与黑顶林莺（Sylvia atricapilla）鸣声线索的影响。研究结果表明，林柳莺在确定繁殖位点时会利用异种个体的鸣声线索。在模拟存在叽喳柳莺的样地中，林柳莺的定居时间更早、个体数量更多；与之相反，黑顶林莺的存在会对林柳莺的定居产生负面影响，提示林柳莺会规避该异种物种。叽喳柳莺与黑顶林莺均会被模拟存在同种个体的样地所吸引，这为这两类物种在繁殖位点选择中存在同种吸引现象提供了实证依据。本实验表明，异种吸引并非仅局限于居留物种与迁徙物种间的相互作用，在迁徙物种之间同样存在该现象。本研究结果揭示了迁徙鸣禽类群在借助社会线索进行栖息地选择决策时，吸引与规避两种机制的协同作用，并强调了社会环境对个体定居行为的正向与负向影响均具备重要研究价值。