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.

精准识别显著线索是适应性应答的关键，但其中涉及的底层感知与认知机制往往尚未被充分阐明。例如，学界长期以来认为，鸟类巢寄生者的寄主会依据外来卵与自身卵的整体颜色差异度来驱逐巢内外来卵，而不考虑外来卵自身的具体色调。本研究针对自然（蓝绿色至棕色）与人工（绿色至紫色）两种卵色梯度测试了寄主的应答行为，结果显示，寄主的驱逐决策仅依据自然卵色梯度下的颜色差异方向与差异程度，而非人工卵色梯度。在自然卵色梯度中，寄主会驱逐棕色卵、接受蓝绿色卵，而不考虑其与自身卵的主观感知整体差异度。与之相对，人工卵色梯度下寄主的应答并未出现显著差异。本研究结果表明，卵识别机制特异性适配于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知接收机制与决策规则的重要性，同时也说明，通过探究表型的自然变异，能够深化我们对识别过程的认知。