Department of Biology, University of Washington, 24 Kincaid Hall, Seattle, WA 98105, USA.
Burke Museum of Natural History and Culture, 4300 15th Ave NE, Seattle, WA 98105, USA.
Integr Comp Biol. 2021 Sep 8;61(2):736-748. doi: 10.1093/icb/icab124.
Hummingbirds have two main foraging strategies: territoriality (defending a patch of flowers) and traplining (foraging over routine circuits of isolated patches). Species are often classified as employing one or the other. Not only have these strategies been inconsistently defined within the behavioral literature, but this simple framework also neglects the substantial evidence for flexible foraging behavior displayed by hummingbirds. Despite these limitations, research on hummingbird foraging has explored the distinct avenues of selection that proponents of either strategy presumably face: trapliners maximizing foraging efficiency, and territorialists favoring speed and maneuverability for resource defense. In earlier studies, these functions were primarily examined through wing disc loading (ratio of body weight to the circular area swept out by the wings, WDL) and predicted hovering costs, with trapliners expected to exhibit lower WDL than territorialists and thus lower hovering costs. While these pioneering models continue to play a role in current research, early studies were constrained by modest technology, and the original expectations regarding WDL have not held up when applied across complex hummingbird assemblages. Current technological advances have allowed for innovative research on the biomechanics/energetics of hummingbird flight, such as allometric scaling relationships (e.g., wing area-flight performance) and the link between high burst lifting performance and territoriality. Providing a predictive framework based on these relationships will allow us to reexamine previous hypotheses, and explore the biomechanical trade-offs to different foraging strategies, which may yield divergent routes of selection for quintessential territoriality and traplining. With a biomechanical and morphofunctional lens, here we examine the locomotor and energetic facets that dictate hummingbird foraging, and provide (a) predictions regarding the behavioral, biomechanical, and morphofunctional associations with territoriality and traplining; and (b) proposed methods of testing them. By pursuing these knowledge gaps, future research could use a variety of traits to help clarify the operational definitions of territoriality and traplining, to better apply them in the field.
领地性（捍卫一片花丛）和巡回觅食（在孤立的花丛之间进行常规巡回）。通常根据物种采用的策略对其进行分类。不仅在行为文献中这些策略的定义不一致，而且这种简单的框架也忽略了蜂鸟表现出的灵活觅食行为的大量证据。尽管存在这些局限性，但有关蜂鸟觅食的研究还是探索了两种策略的支持者可能面临的不同选择途径：巡回觅食者最大限度地提高觅食效率，而领地性觅食者则优先考虑速度和机动性以保护资源。在早期的研究中，主要通过翅膀圆盘负载（体重与翅膀扫过的圆形面积之比，WDL）和预测悬停成本来检验这些功能，预计巡回觅食者的 WDL 低于领地性觅食者，因此悬停成本较低。虽然这些开创性的模型在当前的研究中仍然发挥着作用，但早期的研究受到技术的限制，并且当应用于复杂的蜂鸟集合体时，WDL 的原始预期并没有得到维持。当前的技术进步使得对蜂鸟飞行的生物力学/能量学进行创新研究成为可能，例如，异速比例关系（例如，翅膀面积-飞行性能）和高爆发提升性能与领地性之间的联系。基于这些关系提供一个预测框架，将使我们能够重新检验以前的假设，并探索不同觅食策略的生物力学权衡，这可能为典型的领地性和巡回觅食提供不同的选择途径。通过生物力学和形态功能学的视角，我们在这里检查了决定蜂鸟觅食的运动和能量方面，并提供了（a）关于与领地性和巡回觅食相关的行为、生物力学和形态功能的预测；和（b）提出了测试它们的方法。通过研究这些知识空白，未来的研究可以使用各种特征来帮助澄清领地性和巡回觅食的操作定义，并在实地更好地应用它们。
