It's not just what you have, but how you use it: solar-positional and behavioral effects on hummingbird color appearance during courtship

Animals exhibit a diversity of colors that can play key roles in mating interactions. However, we presently lack an understanding of the relative importance of the environment, behavior, and natural reflective properties of colorful ornaments on an individual’s color appearance during mating-displays. We investigated interactions among structurally-based plumage, display environments, and courtship shuttle displays of male Costa's hummingbirds (Calypte costae) to test how these elements may differentially contribute to color appearance during shuttles. Male position relative to the sun was the strongest predictor of color appearance, with shuttle behaviors and feather reflectance playing smaller roles. Further, male solar orientation and shuttling behavior (e.g. shuttle width) were repeatable among displays, whereas male color appearance mostly was not. These results emphasize the contributions of behavior and environment to color-signaling and suggest that relying on reflectance measurements of colorful ornaments alone provides an incomplete picture of ecologically relevant visual phenotypes of displaying animals.

动物拥有多样的体色，此类体色在交配互动中可发挥关键作用。然而，目前学界仍缺乏对环境、行为以及色彩装饰的自然反射特性在动物交配展示过程中对个体体色呈现的相对重要性的认知。本研究针对科斯塔蜂鸟（Calypte costae）雄鸟的结构色羽饰（structurally-based plumage）、展示环境与求爱穿梭展示（courtship shuttle displays）之间的相互作用展开调查，以探究这些因素在穿梭展示过程中如何差异化地影响体色呈现。研究结果表明，雄鸟相对于太阳的位置是体色呈现最有力的预测因子，而穿梭行为与羽毛反射率的影响相对较小。此外，雄鸟的太阳方位与穿梭行为（如穿梭宽度）在多次展示中具有可重复性，而雄鸟的体色呈现则大多不具备可重复性。上述研究结果凸显了行为与环境对色彩信号传递的贡献，并提示仅依靠色彩装饰的反射率测量，无法完整呈现展示动物的生态相关视觉表型。