Biological hypotheses predicting patterns of offspring begging typically concern the covariance with hunger and/or development at specific hierarchical levels. For example, hunger drives within-individual patterns of begging, but begging also drives food intake among individuals within broods, and begging and food intake can covary positively or negatively among genotypes or broods. Testing biological phenomena that occur at multiple levels, therefore, requires the partitioning of covariance between traits of interest to ensure that each level-specific relationship is appropriately assessed. We performed a partial cross-fostering study on a wild population of great tits (Parus major), then used multivariate mixed models to partition variation and covariation in nestling begging effort and two metrics of nestling hunger within versus among individual nestlings and broods. At the within-individual level, we found that nestlings begged more intensely when hungrier (positive correlation between begging and hunger). However, among individuals, nestlings that were fed more frequently also begged more intensely on average (negative correlation between begging and hunger). Variation in nestling mass did not give rise to the negative correlation between begging and hunger among nestlings, but we did find that lighter nestlings begged more intensely than their heavier biological siblings, suggesting that this effect may be driven by a genetic component linked to offspring size. Our study illustrates how patterns of covariance can differ across biological levels of analysis and addresses biological mechanisms that could produce these previously obscured patterns.

中文翻译：

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不同生物学水平的雏鸟乞讨行为和饥饿的（共）变异的新来源

预测后代乞讨模式的生物学假设通常涉及饥饿和/或特定层次结构的发育的协方差。例如，饥饿会驱使个体内部的乞讨方式产生影响，但乞讨也会推动育雏个体之间的食物摄取，而乞讨和食物摄取会在基因型或育雏群体之间产生积极或消极的共鸣。因此，要测试在多个级别上发生的生物现象，需要对目标特征之间的协方差进行划分，以确保正确评估每个级别特定的关系。我们对大山雀（Parus major）的野生种群进行了部分交叉培育研究），然后使用多元混合模型划分巢式乞讨工作量的变异和协变，以及各个巢内和巢内的巢内饥饿感的两个指标。在个体内部，我们发现饥饿时雏鸟的乞讨更加强烈（乞讨和饥饿之间呈正相关）。但是，在个体中，喂养频率较高的雏鸟的平均乞讨强度也更高（乞讨与饥饿之间呈负相关）。雏鸟质量的变化并没有引起雏鸟之间的乞讨和饥饿之间的负相关性，但是我们确实发现，较轻的雏鸟比其较重的生物兄弟姐妹的乞讨程度更强，这表明这种影响可能是由与后代大小有关的遗传因素驱动的。 。