Dissertation Research: Dead-Leaf Foraging Specialization by Tropical Forest Birds

这项研究将记录不同热带鸟类群落特有的极端觅食专门化，然后测试关于维持这种专门化的具体假设。在亚马逊雨林的两个地点，每个地点都发现了十几种鸟类，主要通过从悬挂在森林下层的卷曲的枯叶中提取节肢动物来觅食。由于枯叶代表离散的资源补丁，这项研究可以量化树叶的可用性和使用，以及可用猎物的丰度。一项初步的实证研究表明，以下预测将在野外捕获的鸟类和节肢动物的一系列室外笼子实验中得到验证：1)枯叶专家对枯叶相对于其他基质有固定的偏好，但对特定类型的预测是灵活的；2)专家在捕获隐藏在枯叶中的猎物方面比共生的多面手更有效率；3)死叶节肢动物对隐藏在这些树叶中有固定的偏好；4)这些节肢动物对鸟类捕食表现出刻板的行为反应，这反过来又影响鸟类的觅食效率。这项研究在两个重要方面与大多数其他食虫鸟类研究不同；第一，食物可获得性和食量是直接测量的，而不是根据取食行为或形态推断的；第二，这种资源系统对实验操作的适应性为评估可能促进专门化的各种过程的作用提供了难得的机会。

This research will document an extreme foraging specialization that is unique to diverse tropical bird communities, and then test specific hypotheses concerning the maintenance of this specialization. A dozen bird species at each of two Amazonian rainforest sites were found to forage primarily by extracting arthropods from curled dead leaves suspended in the forest understory. Because the dead leaves represent discrete resource patches, this research can quantify leaf availability and use, as well as the abundance of available prey. A preliminary empirical study suggests the following predictions to be tested in a series of outdoor cage experiments on wild-caught birds and arthropods: 1) dead leaf specialists have fixed preferences for dead leaf vs. other substrates, but are flexible with respect to particular types; 2) specialists are more efficient than co-occurring generalists at capturing prey hiding in dead leaves; 3) dead-leaf arthropods have fixed preferences for hiding in these leaves; and 4) these arthropods exhibit stereotyped behavioral responses to bird predation that in turn influence the bird's foraging efficiency. This study differs from most other insectivorous bird studies in two important ways; first, food availability and diets are measured directly rather than inferred from feeding behavior or morphology, and second, the amenability of this resource system to experimental manipulation provides a rare opportunity to evaluate the role of the various processes that may promote specialization.