Vegetation of tropical dry ecosystems is represented by patches of plants with different photosynthetic pathways. We used C and N stable isotope mixing models to assess the relative importance of CAM and C3 vegetation as direct or indirect sources of food for birds in a Neotropical semiarid zone. We analyzed tissues from 26 bird species encompassing a broad array of feeding habits in the dry and rainy seasons. Although CAM plants are important elements of our study site, their use as food was mainly restricted to some plant‐eating and omnivorous bird species. “Intermediate” or “High” dependence on CAM food was observed in only 7 species: three frugivores, one nectarivore, one granivore, and two omnivores. Instead, C3‐derived food sustained most of the bird species studied, even some for which dependence on CAM‐derived food was reported in studies using other methodological approaches. Consumption of C3 insects extended to the entire assemblage of birds, including plant‐eating species. Our findings highlight the importance of maintaining vegetation heterogeneity in arid zones for animal communities and the need to provide increasing protection measures to woody C3 species, as their local demand for firewood is rapidly increasing.

中文翻译：

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C3和CAM食物途径对新热带半干旱地区鸟类的饮食重要性

热带干旱生态系统的植被以具有不同光合途径的植物斑块为代表。我们使用C和N稳定同位素混合模型来评估CAM和C3植被作为新热带半干旱地区鸟类食物的直接或间接来源的相对重要性。我们分析了26种鸟类的组织，这些组织涵盖了在干燥和雨季的广泛采食习惯。尽管CAM植物是我们研究地点的重要元素，但它们作为食物的用途主要仅限于某些以植物为食和杂食性鸟类。仅在7个物种中观察到对CAM食物的“中度”或“高度”依赖性：3个节食动物，1个油桃，1个食肉动物和2个杂食动物。取而代之的是，源自C3的食物维持了所研究的大多数鸟类，甚至在使用其他方法学的研究中也报道了依赖于CAM的食物。C3昆虫的消费扩展到鸟类的整个种群，包括以植物为食的物种。我们的发现凸显了在干旱地区保持动物群落的异质性对于动物群落的重要性，以及由于当地对木柴的需求迅速增加，需要对木质C3物种提供越来越多的保护措施。