本期Nature Communications上发表的一篇论文报告说，杜鹃会在同一寄主巢中反复下蛋，目的是增加它们的蛋被寄主父母接受的可能性。这项研究表明，这一方法会扰乱“养父母”用来识别它们自己的蛋的认知过程，降低杜鹃的蛋被拒绝的风险。
很多种杜鹃在其他鸟的巢中下蛋，并且形成了逃避被拒绝的一些策略，如模仿寄主蛋的外观。为此，作为寄主的鸟也掌握了区分它们自己的蛋与杜鹃蛋的方法。除了利用以前有关它们自己蛋的知识外，它们似乎还会寻找在颜色、图案和大小上的差别，然后将不符合它们内部模板的蛋扔掉。通过研究撒哈拉以南非洲的一种本地杜鹃和它们的寄主（褐头鹪莺），Martin Stevens及同事发现，任何一个巢中所下的杜鹃蛋的数量的增加，都会导致寄主鸟的这些分辨过程的扰乱以及寄生蛋更大程度的接受。该研究小组还发现，寄生蛋的数量越大，寄主就需要在颜色上有更大差别才能正确识别它们自己的蛋和拒绝杜鹃的蛋。
生物谷推荐的英文摘要
Nature Communications DOI:10.1038/ncomms3475
Repeated targeting of the same hosts by a brood parasite compromises host egg rejection
Martin Stevens，Jolyon Troscianko & Claire N. Spottiswoode
Cuckoo eggs famously mimic those of their foster parents to evade rejection from discriminating hosts. Here we test whether parasites benefit by repeatedly parasitizing the same host nest. This should make accurate rejection decisions harder， regardless of the mechanism that hosts use to identify foreign eggs. Here we find strong support for this prediction in the African tawny-flanked prinia (Prinia subflava)， the most common host of the cuckoo finch (Anomalospiza imberbis). We show experimentally that hosts reject eggs that differ from an internal template， but crucially， as the proportion of foreign eggs increases， hosts are less likely to reject them and require greater differences in appearance to do so. Repeated parasitism by the same cuckoo finch female is common in host nests and likely to be an adaptation to increase the probability of host acceptance. Thus， repeated parasitism interacts with egg mimicry to exploit cognitive and sensory limitations in host defences.
