Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida 32611, USA.
Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
Ecol Appl. 2016 Dec;26(8):2381-2387. doi: 10.1002/eap.1456.
Elevational migration is a widespread phenomenon in tropical avifauna but it is difficult to identify using traditional approaches. Hydrogen isotope (δ H) values of precipitation decrease with elevation so δ H analysis of multiple bird tissues with different isotopic incorporation rates may be a reliable method for characterizing seasonal elevational migration. Here we compare δ H values in metabolically inert (feathers and claws) and metabolically active (whole blood) tissues to examine whether an upslope migration occurs prior to the breeding season in the Yungas Manakin (Chiroxiphia boliviana). We compare results from C. boliviana with data from a known elevational migrant, the Streak-necked Flycatcher (Mionectes striaticollis). Opposite to our expectations, tissue δ H values increased over time, largely reflecting seasonal patterns in precipitation δ H rather than elevational effects; linear mixed-effects models with strongest support included ordinal date, tissue type, and elevation. This seasonal increase in precipitation δ H is a general phenomenon in both tropical and temperate mountain ranges. We use these data to propose a hypothetical framework that predicts different patterns in tissue δ H values collected in different seasons from residents and elevational migrants. This framework can serve as a reference for future studies that assess elevational migration in birds and other animals.
海拔迁移是热带鸟类中广泛存在的现象，但使用传统方法很难识别。降水的氢同位素（δH）值随海拔升高而降低，因此分析具有不同同位素掺入率的多种鸟类组织的δH值可能是表征季节性海拔迁移的可靠方法。在这里，我们比较了代谢惰性（羽毛和爪子）和代谢活跃（全血）组织中的 δH 值，以检验在 Yungas 丛巴纳雀（Chiroxiphia boliviana）的繁殖季节之前是否发生了上坡迁移。我们将 C. boliviana 的结果与已知的海拔迁徙者条纹颈蝇虎（Mionectes striaticollis）的数据进行了比较。与我们的预期相反，组织的 δH 值随时间增加，主要反映了降水 δH 的季节性模式，而不是海拔效应；具有最强支持的线性混合效应模型包括有序日期、组织类型和海拔。这种降水 δH 的季节性增加是热带和温带山脉的普遍现象。我们使用这些数据提出了一个假设框架，预测了在不同季节从居民和海拔迁徙者收集的组织 δH 值的不同模式。这个框架可以作为未来研究鸟类和其他动物海拔迁移的参考。
