Data from: Elevational replacement of two Himalayan titmice: interspecific competition or habitat preference?

Elevational species replacement is a widely documented pattern in montane species. Although interspecific competition has been shown to be important in setting species elevational limits in tropical habitats, its effect in species of temperate regions is poorly studied. We tested the role of interspecific competition for space in the breeding season and for food in the non-breeding season in mediating the distribution of two resident titmice species in the Himalayas. We show that high elevation green-backed tits Parus monticolus are behaviourally dominant over low elevation cinereous tits Parus cinereus in both song playback and feeder trials. Despite being subordinate, at their elevational upper limit, cinereous tits occur in sympatry in human modified habitats. Our study suggests that the loss of natural habitats in the sympatric zone, not interspecific competition, might be limiting the distribution of the high-elevation green-backed tits and facilitating an upward range shift through human association in cinereous tits.

物种海拔替代格局是山地类群中被广泛记录的生态分布模式。尽管已有研究证实种间竞争在热带生境中对物种海拔分布界限的塑造发挥着重要作用，但针对温带类群的相关研究仍较为匮乏。本研究以喜马拉雅地区的两种留居山雀为研究对象，探究了繁殖季空间资源竞争与非繁殖季食物资源竞争在调控二者分布格局中的作用。研究发现，在鸣声回放实验与投食器实验中，高海拔的绿背山雀（Parus monticolus）均表现出优于低海拔灰山雀（Parus cinereus）的行为优势。尽管灰山雀处于行为劣势，但在其自身海拔分布上限处，二者会在人为改造生境中形成同域分布。本研究表明，同域分布区的自然生境丧失而非种间竞争，可能是限制高海拔绿背山雀分布的关键因素，同时也推动了灰山雀通过与人类活动的关联实现分布范围的向上扩张。