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.

晚成雏鸟类（altricial birds）雏鸟的部分特征色彩可能会影响亲鸟的食物分配，因为这类色彩能够反映雏鸟的身体状况或饥饿程度。现有越来越多的证据表明，乞食特征（begging traits）的色彩与雏鸟的生存表现存在关联。然而，关于饥饿水平对雏鸟色彩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）雏鸟的饥饿感知，并评估其对雏鸟口角褶（rictal flanges）、口腔及体肤色彩的影响。
研究发现，相较于对照组同巢雏鸟，经盐酸赛庚啶处理的雏鸟，其口角褶色彩更为醒目，色视觉对比度（chromatic visual contrast）更高、紫外着色（UV coloured）更强而黄色着色（yellow coloured）更弱。与之相反，实验组雏鸟的口腔色彩则呈现出黄色着色更强、紫外着色更弱的特征。
本药理学实验对体重（body mass）与体肤的部分色彩组分——色视觉对比度（chromatic visual contrast）与消色视觉对比度（achromatic visual contrast）、紫外色饱和度（UV–chroma）及黄色色饱和度（Yellow–chroma）——以及口角褶的部分色彩组分——色视觉对比度、紫外色饱和度及黄色色饱和度——之间的关联强度产生了影响，但未对口腔色彩产生显著作用。
综合上述结果可知，盐酸赛庚啶对雏鸟色彩的影响可能存在两种介导路径：对口角褶与体肤色彩的影响由雏鸟饥饿水平提升所介导，而对口腔色彩的影响则由雏鸟身体状况改善所介导。