Three Excel data show the experimental results detail from Common cuckoo females remove more conspicuous eggs during parasitism

Avian obligate brood parasites gain an advantage by removing the eggs of the cuckoos who have already visited the nest, which can increase the chances of survival for their offspring. Conversely, to prevent their eggs from being picked up by the next parasitic cuckoo, they need to take some precautions. Egg mimicry and egg crypsis are two alternative strategies to prevent the parasitized egg from being picked up by another parasitic cuckoo. Here, we tested whether the egg crypsis hypothesis has a preventative effect when common cuckoos (<i>Cuculus canorus</i>) parasitize their Oriental reed warbler (<i>Acrocephalus orientalis</i>) hosts. We designed two experimental groups with different crypsis effects to induce common cuckoos to lay eggs and observed whether the cuckoos selectively picked up the experimental eggs with low crypsis levels in the process of parasitism. Our results supported the egg crypsis hypothesis; the observed cuckoos significantly preferred to select the more obvious white model eggs. This shows that even in an open nest, eggs that are adequately hidden can also be protected from being picked up by cuckoo females during parasitism so as to increase the survival chance of their own parasitic eggs.

专性巢寄生鸟类会通过移除已到访该巢的其他杜鹃卵来获得生存优势，此举可提升自身后代的存活概率。反之，为避免自身卵被后续寄生的杜鹃移除，宿主需采取相应防范策略。卵拟态（egg mimicry）与卵隐蔽性（egg crypsis）是两种可阻止寄生卵被其他杜鹃移除的备选策略。本研究以大杜鹃（*Cuculus canorus*）寄生东方大苇莺（*Acrocephalus orientalis*）宿主系统为对象，验证卵隐蔽性假说是否具有防范效应。我们设置了两组具有不同隐蔽性效果的实验组以诱导大杜鹃产卵，并观察杜鹃在寄生过程中是否会选择性移除隐蔽性较低的实验卵。研究结果证实了卵隐蔽性假说：受试大杜鹃显著偏好选择辨识度更高的白色模拟卵。这表明即便在开放式鸟巢中，充分隐蔽的卵也可在寄生过程中免遭雌性杜鹃移除，从而提升自身寄生卵的存活概率。