Egg rejection and clutch phenotype variation in the plain prinia (Prinia inornata)

Avian hosts of brood parasites can evolve anti-parasitic defenses to recognize and reject foreign eggs from their nests. Theory predicts that higher inter-clutch and lower intra-clutch variation in egg appearance facilitates hosts to detect parasitic eggs as egg-rejection mainly depends on the appearance of the egg. Therefore, we predict that egg patterns and rejection rates will differ when hosts face different intensity of cuckoo parasitism. We tested this prediction in two populations of the plain prinia (Prinia inornata): Guangxi in mainland China with high diversity and density of cuckoo species, and Taiwan where there is only one breeding cuckoo species, the Oriental cuckoo (Cuculus optatus). As expected, egg patterns were similar within clutches but different among clutches (polymorphic eggs) in the mainland population, while the island population produced more uniform egg morphs. Furthermore, the mainland population showed a high rate of egg rejection, while the island populatio...巢寄生生物（brood parasites）的鸟类宿主可演化出抗寄生防御策略，以识别并移除巢穴中的外来卵。理论预测，卵外观的窝间变异更高、窝内变异更低时，更便于宿主识别寄生卵——因为卵的移除行为主要依赖卵的外观特征。因此我们推测，当宿主面临不同强度的杜鹃寄生压力时，其卵的花纹与卵移除率会存在差异。我们以纯色山鹪莺（Prinia inornata）的两个种群验证了这一推测：其一为中国大陆广西种群，该区域杜鹃物种多样性与种群密度均较高；其二为台湾种群，该区域仅存在一种繁殖杜鹃——东方杜鹃（Cuculus optatus）。正如预期，大陆种群的卵外观呈现“窝内相似、窝间相异”的特征（即多态卵），而岛屿种群的卵形态则更为统一。此外，大陆种群的卵移除率较高，而岛屿种群……