Many hosts of obligate brood‐parasitic birds use variation in the coloration and pattern of eggshells to identify and reject foreign eggs from their nests. However, egg‐rejection behavior of several hosts is not tightly predicted by the modeled output of overall avian‐perceivable chromatic differences between foreign and host eggs. This demands a re‐investigation into the proximate sensory cues and perceptual processes used for egg recognition. One plausible mechanism is that rejection by hosts depends on the relative stimulation of one (or a combination) of their photoreceptors when comparing their own and parasitic eggs (i.e., self‐referencing). To test this, we placed dark‐blue egg models (with a known ~ 50% rejection rate) in nests of American Robins (Turdus migratorius), which are occasional hosts of Brown‐headed Cowbirds (Molothrus ater). We found that relative metrics of individually repeatable size or shape and overall avian‐perceivable differences in color between American Robin eggs and model eggs did not explain the probability of an experimental egg being rejected. However, despite a limited R² value, hosts were significantly more likely to reject a model egg when the estimated contrast between their own egg and the model egg was greater for the blue (SWS) photoreceptor. These results are consistent with female American Robins using a simple physiological algorithm that would confer widespread benefits by reducing the likelihood of rejecting their own eggs, while still eliminating parasitic eggs because of their dissimilar novel coloration.

中文翻译：

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自指表型匹配不能很好地预测美国人罗宾斯的卵子排斥反应

许多寄主寄生鸟类的宿主利用蛋壳的颜色和图案变化来识别和拒绝巢中的异卵。但是，通过外来鸡蛋和宿主鸡蛋之间总体禽可感知色差的模型输出，不能严格预测几个宿主的鸡蛋排斥行为。这要求对用于蛋识别的最接近的感觉线索和知觉过程进行重新研究。一种可能的机制是，宿主在将其自身卵与寄生卵进行比较时（即自我参照），其排斥取决于一种或多种感光器的相对刺激。为了测试这一点，我们在美国知更鸟（Turdus migratorius）的巢中放置了深蓝色的卵模型（已知的排斥率约为50％）），它们偶尔是棕头牛bird（Molothrus ater）的寄主。我们发现，美国知更鸟蛋和模型蛋之间的个体可重复大小或形状以及总体鸟类可感知的颜色差异的相对度量标准不能解释实验鸡蛋被拒绝的可能性。然而，尽管R ²有限值，当蓝色（SWS）感光体的自身蛋与模型蛋之间的估计对比度更大时，宿主明显更可能拒绝模型蛋。这些结果与美国雌性罗宾斯使用简单的生理算法是一致的，该算法将通过减少拒绝自己的卵的可能性而赋予广泛的收益，同时由于它们的新颖奇异的颜色而仍消除了寄生卵。