Data from: Decoding colouration of begging traits by the experimental addition of the appetite enhancer cyproheptadine hydrochloride in magpie (Pica pica) nestlings

The colouration of some traits in nestlings of altricial birds may influence parental food allocation as it may reflect physical condition or hunger. There is increasing evidence of the relationship between colouration of begging traits and nestling performance. However, evidence of the influence of hunger level on nestling colouration is scarce, mainly because of difficulty of distinguishing between the effects of physical condition and hunger levels. Here, we used the appetite stimulant cyproheptadine hydrochloride to increase the sensation of hunger of magpie (Pica pica) nestlings for eight days and assessed the effect on the colouration of rictal flanges, mouth and body skin. We found that nestlings administered with cyproheptadine had flanges more conspicuous (chromatic visual contrast), more UV coloured and less yellow coloured than their control nestmates. Conversely, mouths of experimental nestlings were more yellow coloured and less UV coloured than controls. Our pharmacological experiment affected the strength of the relationship between body mass and some colour components of body skin (chromatic and achromatic visual contrasts, UV–chroma and Yellow–chroma) and of rictal flanges (chromatic visual contrasts, UV–chroma and yellow–chroma), but not for mouth colouration. These results taken together suggest that the effect of the cyproheptadine on nestling colourations is probably mediated by an increase in hunger levels of nestlings for rictal flanges and body skin colourations, and by an increase in physical condition in the case of mouth coloration.

晚成雏鸟（altricial birds）幼鸟的部分性状体色可能影响亲代的食物分配，因其体色可反映幼鸟的身体状况或饥饿程度。目前已有越来越多证据表明，乞食性状（begging traits）的体色与幼鸟表现存在关联。然而，关于饥饿水平对幼鸟体色影响的研究证据仍较为匮乏，主要原因在于难以区分身体状况与饥饿水平各自产生的效应。本研究通过食欲刺激剂盐酸赛庚啶（cyproheptadine hydrochloride），在8天内提升喜鹊（Pica pica）幼鸟的饥饿感，并评估其对幼鸟口角褶（rictal flanges）、口腔及体皮肤色的影响。研究发现，与对照组同窝幼鸟相比，喂食盐酸赛庚啶的实验组幼鸟的口角褶更具醒目性（色视觉对比度（chromatic visual contrast）更高）、UV色度更强、黄色色度更低。与之相反，实验组幼鸟的口腔颜色黄色色度更高、UV色度更低。本药理学实验对体重与体皮肤色部分组分（色视觉对比度、消色视觉对比度（achromatic visual contrast）、UV色度及黄色色度）以及口角褶（色视觉对比度、UV色度与黄色色度）之间的关联强度产生了影响，但未对口腔体色产生作用。综合以上结果表明，盐酸赛庚啶对幼鸟体色的影响可能存在不同介导路径：对口角褶与体皮肤色的影响由幼鸟饥饿水平提升所介导，而对口腔体色的影响则由身体状况改善所介导。