SELVA: Investigación para la Conservación en el Neotrópico, DG 42A #20-37, 111311, Bogotá D.C., Colombia.
Committee on Evolutionary Biology, The University of Chicago, Culver Hall 402, Chicago, Illinois, 60637, USA.
Ecol Appl. 2022 Jan;32(1):e02481. doi: 10.1002/eap.2481. Epub 2021 Nov 21.
The tropical Andes are characterized by extreme topographic and climatic complexity, which has likely contributed to their outstanding current species diversity, composed of many range-restricted species. However, little is known about how the distribution and abundance of highly mobile organisms, like long-distance migratory birds, varies across different land covers, elevations, and climatic conditions within the Andes. We conducted 1,606 distance-sampling point counts across the Colombian Andes, spanning elevations from 253 to 3,708 m, a range of precipitation regimes and representative land covers. We then employed a novel application of a multispecies hierarchical modeling approach to evaluate how elevation, local land cover, aboveground woody biomass, cloud cover, precipitation, and seasonality in precipitation shape the abundance of the migratory land bird community in the Andes. We detected 1,824 individuals of 29 species of migratory land birds, six of which were considered incidental in our study region. We modeled the abundance of the remaining 23 species, while considering observer and time of day effects on detectability. We found that both elevation and land cover had an overriding influence on the abundance of migratory species across the Andes, with strong evidence for a mid-elevation peak in abundance, and species-specific responses to both variables. As a community, migratory birds had the highest mean abundance in shade coffee plantations, secondary forest, and mature forest. Aboveground woody biomass did not affect the abundance of all species as a group, but a few showed strong responses to this variable. Contrary to predictions of a positive correlation between abundance and precipitation, we found no evidence for community-level responses to precipitation, aside for a weak tendency for birds to select areas with intermediate levels of precipitation. This novel use of a multispecies model sheds new light on the mechanisms shaping the winter distribution of migratory birds and highlights the importance of elevation and land cover types over climatic variables in the context of the Colombian Andes.
安第斯热带地区的地形和气候非常复杂，这可能是其当前物种多样性极高的原因之一，其中包括许多分布范围有限的物种。然而，对于像长途迁徙鸟类这样高度移动的生物，它们在安第斯山脉内不同的土地覆盖、海拔和气候条件下的分布和丰度如何变化，我们知之甚少。我们在哥伦比亚安第斯山脉进行了 1606 个距离抽样点计数，海拔范围从 253 米到 3708 米，涵盖了不同的降水模式和有代表性的土地覆盖类型。然后，我们采用一种新的多物种层次模型方法来评估海拔、当地土地覆盖、地上木质生物质、云量、降水以及降水季节性如何影响安第斯山脉迁徙陆地鸟类群落的丰度。我们检测到了 1824 只 29 种迁徙陆地鸟类的个体，其中 6 种在我们的研究区域被认为是偶然出现的。我们对其余 23 种鸟类的数量进行建模，同时考虑了观察者和一天中时间对可检测性的影响。我们发现，海拔和土地覆盖对安第斯山脉迁徙物种的丰度都有至关重要的影响，在中海拔处存在丰度的强烈峰值，并且物种对这两个变量的反应也具有特异性。作为一个群落，迁徙鸟类在遮荫咖啡种植园、次生林和成熟林中有最高的平均丰度。地上木质生物质并没有对所有物种作为一个群体的丰度产生影响，但有几个物种对这个变量表现出强烈的反应。与丰度与降水之间存在正相关的预测相反，我们没有发现鸟类群落对降水有任何一致的反应，除了鸟类对中等降水水平的微弱偏好。这种多物种模型的新应用为塑造迁徙鸟类冬季分布的机制提供了新的认识，并强调了在哥伦比亚安第斯山脉的背景下，海拔和土地覆盖类型比气候变量更为重要。
