The rejection of parasitic eggs by hosts of avian brood parasites is one of the most common and effective defenses against parasitism. Despite its adaptive significance, egg rejection often shows substantial intraspecific variation: some individuals are more likely to remove or abandon parasitic eggs than others. Understanding variation in egg rejection requires that we study factors linked to the ability to perceive parasitic eggs as well as factors that may influence the rejection of a foreign egg once it has been recognized. Here, we asked what cognitive, physiological, and life-history factors explained variation in the rejection of model eggs by American robin (Turdus migratorius) females. We found that the probability of egg rejection was related to the clutch size at the time of parasitism: In support of Weber's law, females with fewer eggs were more likely to reject the model eggs. In turn, females with greater mass and higher corticosterone levels were less likely to reject eggs, and egg rejection probability was negatively related to incubation progress. Our data thus suggest that proximate predictors of an individual's egg rejection behavior include the cognitive environment of the nest, life-history factors, as well as the physiological state of the subject. However, much of the statistical variation in the egg rejection responses of robins to the model eggs remained unexplained. Future experiments should aim to test the causal roles of these and other factors in generating within- and among-individual variation in the rejection of parasitic eggs. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

中文翻译：

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禽卵寄生虫宿主卵排斥行为变化的最接近预测因子。

禽卵寄生虫宿主对寄生虫卵的排斥是对寄生虫病最常见，最有效的防御措施之一。尽管它具有适应性的意义，但卵排斥通常表现出种内差异很大：与其他人相比，某些个体更可能去除或放弃寄生卵。了解卵排斥的变化要求我们研究与感知寄生卵的能力有关的因素，以及一旦被识别就可能影响异卵排斥的因素。在这里，我们问到什么认知，生理和生活史因素可以解释美国知更鸟（Turdus migratorius）雌性对卵的排斥反应。我们发现，在寄生虫发生时，排卵的可能性与离合器的大小有关：为了支持韦伯定律，卵较少的雌性更有可能拒绝模型卵。反过来，质量更大，皮质酮水平更高的雌性卵子拒绝的可能性较小，卵卵排斥的可能性与孵化进度呈负相关。因此，我们的数据表明，个体卵子排斥行为的最接近预测因素包括巢的认知环境，生活史因素以及受试者的生理状态。然而，知更鸟对模型卵的卵排斥反应的许多统计变化仍无法解释。未来的实验应旨在测试这些和其他因素在产生寄生卵排斥中个体内和个体间变异的因果作用。（PsycInfo数据库记录（c）2020 APA，保留所有权利）。