Color and spatial vision are critical for recognition and discrimination tasks affecting fitness, including finding food and mates and recognizing offspring. For example, as a counter defense to avoid the cost of raising the unrelated offspring of obligate interspecific avian brood parasites, many host species routinely view, recognize, and remove the foreign egg(s) from their nests. Recent research has shown that host species visually attend to both chromatic and spatial pattern features of eggs; yet how hosts simultaneously integrate these features together when recognizing eggs remains an open question. Here, we tested egg rejection responses of American robins (Turdus migratorius) using a range of 3D-printed model eggs covered with blue and yellow checkered patterns differing in relative square sizes. We predicted that robins would reject a model egg if they could visually resolve the blue and yellow squares as separate features or accept it if the squares blended together and appeared similar in color to the natural blue-green color of robin eggs as perceived by the avian visual system. As predicted, the probability of robins rejecting a model egg increased with greater sizes of its blue and yellow squares. Our results suggest that chromatic visual acuity and viewing distance have the potential to limit the ability of a bird to recognize a foreign egg in its nest, thus providing a limitation to host egg recognition that obligate interspecific avian brood parasites may exploit.

中文翻译：

---

视力和卵空间色度对比预测美国知更鸟的卵排斥行为

颜色和空间视觉对于识别和歧视影响健康的任务至关重要，包括寻找食物和伴侣以及识别后代。例如，作为一种反防御措施，以避免增加专性种间禽亲寄生虫的无关后代的成本，许多寄主物种通常会查看，识别并从其巢中除去外来卵。最近的研究表明，寄主物种在视觉上既观察到鸡蛋的色度特征，又观察到了空间特征。然而，主机在识别卵子时如何同时将这些功能集成在一起仍然是一个悬而未决的问题。在这里，我们测试了美国知更鸟（Turdus migratorius）使用一系列3D打印的模型鸡蛋，这些鸡蛋上覆盖着相对方形大小不同的蓝色和黄色方格图案。我们预测知更鸟如果能将蓝色和黄色正方形可视化地分辨为单独的特征，或者如果正方形混合在一起并看起来与禽类感知到的知更鸟蛋的天然蓝绿色相似，则它们会拒绝模型卵。视觉系统。如所预测的，知更鸟拒绝模型蛋的可能性随着其蓝色和黄色方块的尺寸增大而增加。我们的结果表明，有色的视敏度和观察距离有可能限制鸟类识别其巢中外来卵的能力，从而为宿主卵的识别提供了限制，而该种卵是专一的种间禽类寄生虫可以利用的。