Data from: Brood parasites lay eggs matching the appearance of host clutches

Interspecific brood parasitism represents a prime example of the co-evolutionary arms race where each party has evolved strategies in response to the other. Here we investigated whether common cuckoos (Cuculus canorus) actively select nests within a host population to match the egg appearance of a particular host clutch. To achieve this goal, we quantified the degree of egg matching using the avian vision modelling approach. Randomization tests revealed that cuckoo eggs in naturally parasitized nests showed lower chromatic contrast to host eggs than those assigned randomly to other nests with egg-laying date similar to naturally parasitized clutches. Moreover, egg matching in terms of chromaticity was better in naturally parasitized nests than it would be in the nests of the nearest active non-parasitized neighbour. However, there was no indication of matching in achromatic spectral characteristics whatsoever. Thus, our results clearly indicate that cuckoos select certain host nests to increase matching of their own eggs with host clutches but only in chromatic characteristics. Our results implicate that the ability of cuckoos to actively choose host nests based on the eggshell appearance imposes a strong selection pressure on host egg recognition.

种间巢寄生（Interspecific brood parasitism）是协同进化军备竞赛的典型范例，双方均演化出针对对方的应对策略。本研究旨在探究大杜鹃（Cuculus canorus）是否会在宿主种群中主动选择巢穴，以使其卵与特定宿主窝卵的外观相匹配。为达成该研究目标，我们采用鸟类视觉建模方法量化了卵匹配度。随机化检验结果显示，自然寄生巢穴内的杜鹃卵与宿主卵的色彩对比度，显著低于随机分配至与自然寄生窝产卵日期相近的其他巢穴的杜鹃卵与宿主卵的色彩对比度。此外，自然寄生巢穴的卵在色彩特性上的匹配度，优于最近的活跃未被寄生邻巢的卵匹配度。但在明度光谱特性方面，未发现任何匹配迹象。综上，本研究结果清晰表明，大杜鹃会选择特定宿主巢穴以提升自身卵与宿主窝卵的匹配度，但仅局限于色彩特性维度。本研究结果还暗示，大杜鹃凭借卵壳外观主动选择宿主巢穴的能力，对宿主的卵识别行为施加了强烈的选择压力。