Data from: Two ways to display: male hummingbirds show different color-display tactics based on sun orientation

Animals exhibit a diversity of ornaments and courtship behaviors, which often co-occur and are used for communication. The sensory drive hypothesis states that these traits evolved and vary due to interactions with each other, the environment, and signal receiver. However, interactions between colorful ornaments and courtship behaviors, specifically in relation to environmental variation, remain poorly understood. We studied male iridescent plumage (gorgets), display behavior, and sun orientation during courtship flights (shuttle displays) in broad-tailed hummingbirds (Selasphorus platycercus), to understand how these traits interact in both space and time to produce the perceived coloration of males. We also tested how gorget coloration varies among males based on their plumage, behavioral, and morphological characteristics. In contrast with previous work on other animals, we found that displaying males did not directionally face the sun, but instead displayed on a continuum of solar orientation angles. The gorgets of males who tended to face the sun during their displays appeared flashier (i.e. exhibited greater color/brightness changes), brighter, and more colorful, whereas the gorgets of males who tended to not face the sun were more consistently reflective (i.e. little color change) and had greater UV reflectance. We found that males who produced consistent colors had larger gorgets, whereas males with flashier gorgets were better able to maintain their angles of orientation towards the female. Our study illustrates how visual traits interact in complex ways with each other and the environment and how males of the same species can use multiple tactics to dynamically display their coloration.

动物演化出多样的装饰性结构与求偶行为，二者往往伴随出现，用于个体间的通讯交流。感觉驱动假说（sensory drive hypothesis）提出，这些性状的演化与变异源于性状间、性状与环境以及信号接收者之间的相互作用。然而，针对色彩装饰结构与求偶行为之间的交互作用，尤其是结合环境变异的相关研究仍较为匮乏。本研究以宽尾煌蜂鸟（Selasphorus platycercus）为研究对象，观测雄性个体的虹彩喉羽（gorgets）、展示行为以及求偶飞行过程中的太阳朝向（穿梭展示shuttle displays），旨在解析这些性状如何在时空维度上相互作用，进而形成雄性个体所呈现的体色特征。本研究同时探究了雄性个体的喉羽色彩如何随其羽毛、行为与形态特征产生差异。与此前针对其他动物的研究结论不同，本研究发现，进行展示的雄性蜂鸟并不会定向朝向太阳，而是在一系列太阳朝向角度范围内开展展示行为。在展示过程中倾向朝向太阳的雄性个体，其喉羽视觉效果更为亮眼（即色彩/亮度变化幅度更大）、亮度更高且色彩更丰富；而倾向于不朝向太阳的雄性个体，其喉羽的反射特性更为稳定（即色彩变化微弱），且紫外反射率更高。本研究还发现，喉羽色彩表现稳定的雄性个体拥有更大的喉羽面积，而喉羽视觉效果亮眼的雄性个体则更擅长维持朝向雌性个体的展示角度。本研究揭示了视觉性状之间以及性状与环境间的复杂交互机制，同时阐明了同一物种的雄性个体可通过多种策略动态呈现其体色特征。