Data from: Egg discrimination along a gradient of natural variation in eggshell coloration

Accurate recognition of salient cues is critical for adaptive responses, but the underlying sensory and cognitive processes are often poorly understood. For example, hosts of avian brood parasites have long been assumed to reject foreign eggs from their nests based on the total degree of dissimilarity in colour to their own eggs, regardless of the foreign eggs’ colours. We tested hosts’ responses to gradients of natural (blue-green to brown) and artificial (green to purple) egg colours, and demonstrate that hosts base rejection decisions on both the direction and degree of colour dissimilarity along the natural, but not artificial, gradient of egg colours. Hosts rejected brown eggs and accepted blue-green eggs along the natural egg colour gradient, irrespective of the total perceived dissimilarity from their own egg’s colour. By contrast, their responses did not vary along the artificial colour gradient. Our results demonstrate that egg recognition is specifically tuned to the natural gradient of avian eggshell colour and suggest a novel decision rule. These results highlight the importance of considering sensory reception and decision rules when studying perception, and illustrate that our understanding of recognition processes benefits from examining natural variation in phenotypes.

精准识别显著线索对于生物体的适应性响应至关重要，但其背后的感官与认知机制却往往尚未得到充分阐明。例如，长期以来学界普遍认为，鸟类巢寄生宿主会依据外源卵与自身卵的整体颜色差异度拒绝巢内的外来卵，且不考虑外源卵自身的具体色调。本研究测试了宿主对两类卵色梯度的响应：一类为自然卵色梯度（蓝绿色至棕褐色），另一类为人工卵色梯度（绿色至紫色）；结果表明，宿主的拒卵决策仅依据自然卵色梯度下的颜色差异方向与程度，而非人工卵色梯度。在自然卵色梯度中，宿主会拒绝棕褐色卵、接受蓝绿色卵，而无论该外源卵与自身卵的整体感知差异度如何。与之相反，宿主在人工卵色梯度下的响应并未随色调变化出现显著差异。本研究结果证实，卵识别机制特异性适配鸟类卵壳颜色的自然梯度，并揭示了一种全新的决策规则。这些研究结果凸显了在感知研究中纳入感官接收与决策规则考量的重要性，并表明，通过考察表型的自然变异，能够深化我们对识别过程的认知。