Departamento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Áridas (EEZA-CSIC), General Segura 1, 04001, Almería, Spain,
Oecologia. 2013 Oct;173(2):399-408. doi: 10.1007/s00442-013-2625-8. Epub 2013 Feb 27.
Chromatic signals of offspring quality have been shown to play a role in parent-offspring communication in diurnal birds, but are assumed to be useless in dim light conditions because colour-based discrimination probably requires more light. A major ecological and evolutionary conundrum in this scenario is why the nestlings of some nocturnal owls display colourful beaks. Here, we test the hypothesis that yellow bill coloration of owlets of the nocturnal little owl Athene noctua may function as a chromatic signal revealing to parents aspects of quality of their offspring. In a first step, we examined physical variation in bill coloration and its covariation with owlet quality. Secondly, we studied parental provisioning in relation to an experimental manipulation of bill coloration of owlets. Bills of owlets showed higher within-nest variation in yellow-red chroma than in brightness. Plasma carotenoid concentration and nestling immunological status were not associated with chromatic or achromatic features of the bill. Interestingly, however, heavier owlets displayed more yellow bills than lighter ones. The effect of bill coloration on parental favouritism changed with brood size. Parents holding large broods preferentially fed owlets with enhanced over reduced yellow bill coloration, whereas those with small broods did not significantly bias feeding in relation to owlet bill coloration. Our results, based on integration of objective spectrophotometric assessment of colour and experimental procedures, confirm that parent little owls use bill coloration to reveal information on owlet body mass to adjust their feeding strategies, thus highlighting the importance of considering potential chromatic signals for a full comprehension of parent-offspring communication processes in nocturnal bird species.
已经表明，在昼行鸟类中，后代质量的色度信号在亲代-后代通讯中发挥作用，但在暗光条件下，这些信号被认为是无用的，因为基于颜色的辨别可能需要更多的光。在这种情况下，一个主要的生态和进化难题是，为什么一些夜行猫头鹰的雏鸟会展示出五颜六色的喙。在这里，我们检验了一个假设，即夜行小鸮 Athene noctua 的雏鸟黄色的喙部颜色可能作为一种色度信号，向亲鸟揭示其后代质量的某些方面。在第一步中，我们检查了喙部颜色的物理变化及其与雏鸟质量的协变。其次，我们研究了亲鸟的育雏行为与雏鸟喙部颜色的实验操纵之间的关系。雏鸟的喙部在黄色-红色色度上显示出更高的巢内变异，而在亮度上则较低。血浆类胡萝卜素浓度和雏鸟的免疫状态与喙部的色度或非色度特征无关。然而，有趣的是，更重的雏鸟的喙部比更轻的雏鸟显示出更多的黄色。喙部颜色对亲鸟偏爱的影响随窝雏数量的变化而变化。拥有较大窝雏的亲鸟更倾向于喂食具有增强的黄色喙部颜色的雏鸟，而那些拥有较小窝雏的亲鸟则不会根据雏鸟喙部颜色显著地偏向于喂食。我们的结果基于对颜色进行客观分光光度评估和实验程序的整合，证实了亲代小鸮利用喙部颜色来揭示有关雏鸟体重的信息，以调整其育雏策略，从而强调了考虑潜在的色度信号对于全面理解夜行鸟类的亲代-后代通讯过程的重要性。
