Asian koels recognize the host, but not their nests, for brood parasitism

Avian brood parasites depend upon finding host nests to lay their eggs. However, how brood parasites find the nests of their hosts and select the nests for parasitism remains mostly unresolved. Here, we examined how a non-evicting brood parasite, the Asian koel (Eudynamys scolopaceus) selects the hosts' nests to lay their eggs. We provided a novel habitat (nest box, n=100) to the Asian koel and its host, the common myna (Acridotheres tristis), at a field site in central Bangladesh. A total of 99 nests across 59 boxes were used by common mynas, of which 21.2% of these nests were parasitized by the Asian koel. Moreover, non-host species, the Oriental magpie robin (Copsychus saularis) (n=8) and jungle myna (Acridotheres fuscus) (n=6) also built nests in the boxes but none of these nests were parasitized. We found that active boxes were significantly more parasitized than inactive nest boxes. Among the active nest boxes, only common myna nests were parasitized by the Asian koel. We found a strong tendency for Asian koel selecting common myna nests more than the non-host species, Oriental magpie robin and jungle myna. Our results provide robust experimental support for the importance of host activity suggesting that Asian koels actively select occupied boxes. Our study shows support for the host imprinting hypothesis, where the Asian koel uses the host activity as a cue to search for potential nests, and then decide whether to parasitize.鸟类巢寄生者依赖寻找到宿主的巢穴以产卵繁育后代。然而，巢寄生者如何定位宿主巢穴并选择适宜巢进行寄生，目前仍未得到充分阐明。在本研究中，我们以非驱逐型巢寄生者——亚洲噪鹃（Eudynamys scolopaceus）为研究对象，探究其选择宿主巢穴产卵的行为机制。我们在孟加拉国中部的一处野外样地中，为亚洲噪鹃及其宿主家八哥（Acridotheres tristis）设置了100个新型人工巢箱。59个巢箱中共计被家八哥筑造了99个巢穴，其中21.2%的家八哥巢穴遭到亚洲噪鹃的寄生。此外，非宿主物种鹊鸲（Copsychus saularis，n=8）和丛林八哥（Acridotheres fuscus，n=6）也在巢箱中筑巢，但所有此类巢穴均未被寄生。研究发现，有宿主活动的巢箱被寄生的概率显著高于无宿主活动的巢箱。在有宿主活动的巢箱中，仅家八哥的巢穴遭到了亚洲噪鹃的寄生。我们发现亚洲噪鹃对家八哥巢穴存在显著的选择偏好，而非鹊鸲与丛林八哥的巢穴。本研究结果为宿主活动的重要性提供了强有力的实验证据，表明亚洲噪鹃会主动选择有宿主活动的巢箱。本研究结果支持宿主印记假说，即亚洲噪鹃以宿主的活动作为线索来搜寻潜在巢穴，并据此判断是否进行寄生。