Parents might use signals of need or of quality to decide food provisioning among their offspring, while the use of one or another signal might depend on food availability. Begging success of nestlings of different quality (i.e., body size) would also depend on food availability, and we here explore the effect of experimental food supply in begging success of nestlings and in provisioning of female hoopoes (Upupa epops), a species with extreme hatching asynchrony and nestlings size hierarchy. We video-recorded food allocation of females, begging success of nestlings of different size, and the social context (i.e., the size category of the other nestlings that were begging for food) during periods when experimental food supply was or was not available in the same nests. We found that when experimental food supplementation was present, begging success of the intermediate, but not that of large or small-sized nestlings, increased. The experiment, however, did not affect the feeding preferences of females toward nestlings of different size. Moreover, when small nestlings were the only ones that were begging for food, their begging success decreased in the experimental period, and females used supplemented prey to feed themselves. Those results, on one hand, confirm the importance of food availability for the begging success of nestlings of particular sizes and, on the other, indicate that females prefer to use extra food for their own rather than for the smallest nestlings. We discuss possible mechanisms explaining the detected experimental effects and the adaptive and nonadaptive explanations of mothers ignoring the small nestlings.

中文翻译：

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父母的食物供应和供给行为：小戴胜雏鸟注定会死亡吗？

父母可能会使用需求或质量信号来决定其后代的食物供应，而一种或另一种信号的使用可能取决于食物的供应情况。不同质量（即体型）的雏鸟乞讨成功也取决于食物的供应情况，我们在这里探讨实验性食物供应对雏鸟乞讨成功和供应雌性戴胜（Upupa epops）的影响，雌性戴胜是一种具有极端行为的物种。孵化异步和雏鸟大小层次结构。我们视频记录了雌鸟的食物分配、不同大小的雏鸟乞讨成功的情况，以及在试验性食物供应可用或不可用期间的社会背景（即乞求食物的其他雏鸟的大小类别）。相同的巢穴。我们发现，当存在实验性食物补充剂时，中间雏鸟的乞讨成功率有所增加，但大型或小型雏鸟的乞讨成功率却没有增加。然而，该实验并没有影响雌性对不同大小雏鸟的摄食偏好。此外，当只有小雏鸟乞食时，实验期间它们的乞食成功率下降，雌鸟会使用补充猎物来喂养自己。这些结果一方面证实了食物供应对于特定大小的雏鸟乞讨成功的重要性，另一方面表明雌鸟更喜欢为自己而不是最小的雏鸟使用额外的食物。我们讨论了解释检测到的实验效果的可能机制，以及母亲忽视小雏鸟的适应性和非适应性解释。