Relatively few studies have examined the interactive effects of ecological factors on physiological responses in wild animals. Nearly all of them have been short-term investigations that did not include experimental manipulations, limiting our ability to understand how climate change will affect natural populations. Using a 10-year brood size manipulation experiment in wild blue tits (Cyanistes caeruleus), we quantified the impact of weather conditions and brood competition on the body mass and structural size (tarsus length) of nestlings just prior to leaving the nest. We found that variation in nestling body mass on day 14 after hatching was explained by an interactive effect between average ambient temperature experienced during nestling period and brood size treatment. Specifically, in control broods nestling body mass was correlated with temperature in a non-linear manner (concave) with the vertex point (maximum body mass) at ca. 13 °C. In contrast, in enlarged broods nestling body mass permanently increased (also non-linearly) as temperature advanced. Our results highlight the importance of considering the effects of brood rearing conditions alongside other environmental factors experienced during growth while investigating early-life environmental effects on body condition.

中文翻译：

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环境温度和育雏大小操作对蓝雀雏鸟体重的交互影响：一项长期研究的探索性分析

相对较少的研究考察了生态因素对野生动物生理反应的交互影响。几乎所有这些都是不包括实验操作的短期调查，这限制了我们了解气候变化将如何影响自然种群的能力。在野生蓝雀 (Cyanistes caeruleus) 中使用为期 10 年的育雏大小操作实验，我们量化了天气条件和育雏竞争对离巢前雏鸟体重和结构大小（跗骨长度）的影响。我们发现孵化后第 14 天雏鸟体重的变化可以通过雏鸟期间经历的平均环境温度和育雏大小处理之间的相互作用来解释。具体来说，在对照雏鸟中，雏鸟的体重以非线性方式（凹形）与温度相关，顶点（最大体重）在 ca。13℃。相比之下，在扩大的雏鸟中，随着温度的升高，体重永久增加（也是非线性的）。我们的研究结果强调了在调查早期环境对身体状况的影响时，考虑育雏条件的影响以及生长过程中经历的其他环境因素的重要性。