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（obligate brood parasites）可通过移除已到访该巢的其他杜鹃卵，提升自身后代的存活概率。与之相对，为避免自身卵被后续寄生的杜鹃移除，这类鸟类需要采取相应防御策略。卵拟态（egg mimicry）与卵隐蔽性（egg crypsis）是两种可替代的防御策略，可避免寄生卵被其他寄生杜鹃移除。本研究以大杜鹃（Cuculus canorus）寄生东方大苇莺（Acrocephalus orientalis）的宿主-寄生系统为模型，验证卵隐蔽性假说（egg crypsis hypothesis）是否具备防御效应。我们设置了两组具有不同隐蔽性梯度的实验卵以诱使大杜鹃产卵，并观察寄生过程中杜鹃是否会选择性移除隐蔽性较低的实验卵。实验结果验证了卵隐蔽性假说：观测到的大杜鹃显著偏好选择醒目白色的模拟卵。这表明即便在开放式巢中，充分隐蔽的卵也能在寄生过程中避免被雌性杜鹃移除，从而提升自身寄生卵的存活概率。