<b>L</b><b>inear markings on eggs as important </b><b>egg </b><b>recognition cues for bunting hosts</b>

This study was conducted in the Liuzhi area (22°13′ N, 106°42′ E), Guizhou, southwest China, from March to August during 2018–2022. The study area is situated in the north temperate monsoon climate zone at altitudes of 1070–1657 m. The study area mainly consists of a karst landscape, with a mosaic of villages, farmland, shrubland, and barren slopes. The preservation of traditional agricultural practices may play an important role in the distribution and reproduction of birds in the area (Zhong et al., 2023). Field experiments were conducted to verify whether the hosts could use these linear markings to recognize parasitic eggs. In these experiments, two sympatric hosts of the common cuckoo, namely the south rock bunting (Emberiza yunnanensis) (which lays eggs with linear markings) and the yellow-throated bunting (Emberiza elegans) (which lays eggs with spot markings), were studied. The results demonstrated that both species of bunting hosts show high rejection rates for plain egg budgerigar (Melopsittacus undulatus) eggs and moderate recognition and rejection abilities for swapped eggs (spot versus linear markings), suggesting that linear markings can serve as a cue for egg recognition in the anti-parasitism of these two hosts. This implied that linear markings, an egg trait of south rock buntings, has an anti-parasitism adaptation function against mimicry by parasites. It was experimentally demonstrated for the first time that the evolution of linear markings on eggs of the hosts of common cuckoos may be an egg-characteristic adaptation against parasitism. Nevertheless, additional research is necessary to verify its generality across different systems.本研究于2018—2022年的3月至8月，在中国西南贵州省六枝地区（北纬22°13′，东经106°42′）开展。该研究区域属于北温带季风气候区，海拔范围为1070~1657米，以喀斯特地貌为主体景观，镶嵌有村落、农田、灌丛与荒坡。传统农耕活动的留存对该区域鸟类的分布与繁衍可能具有重要意义（Zhong等，2023）。 为验证宿主能否利用线性斑纹识别寄生卵，本研究开展了野外实验。实验选取大杜鹃（common cuckoo）的两种同域宿主作为研究对象：分别为产线性斑纹卵的南岩鹀（Emberiza yunnanensis），以及产斑点斑纹卵的黄喉鹀（Emberiza elegans）。结果显示，两种鹀类宿主对纯色虎皮鹦鹉（Melopsittacus undulatus）卵均表现出较高的拒卵率，而对交换后的卵（斑点斑纹vs线性斑纹）则具备中等强度的识别与拒卵能力，表明线性斑纹可作为这两种宿主开展抗寄生行为时的卵识别关键线索。这意味着南岩鹀卵的线性斑纹这一性状，具备抵御寄生物拟态的抗寄生适应功能。本研究首次通过实验证实，大杜鹃宿主卵上的线性斑纹演化，可能是一种针对寄生行为的卵特征适应性策略。不过仍需开展更多研究以验证该结论在不同生态系统中的普适性。