Data from: Food supplementation mitigates dispersal-dependent differences in nest defence in a passerine bird.

Dispersing and non-dispersing individuals often differ in phenotypic traits (e.g. physiology, behaviour), but to what extent these differences are fixed or driven by external conditions remains elusive. We experimentally tested whether differences in nest-defence behaviour between dispersing and non-dispersing individuals changed with local habitat quality in collared flycatchers, by providing additional food during the nestling rearing period. In control (non-food-supplemented) nests, dispersers were less prone to defend their brood compared with non-dispersers, whereas in food-supplemented nests, dispersing and non-dispersing individuals showed equally strong nest defence. We discuss the importance of dispersal costs versus adaptive flexibility in reproductive investment in shaping these differences in nest-defence behaviour between dispersing and non-dispersing individuals. Irrespective of the underlying mechanisms, our study emphasizes the importance of accounting for environmental effects when comparing traits between dispersing and non-dispersing individuals, and in turn assessing the costs and benefits of dispersal.扩散个体与非扩散个体通常在表型性状（phenotypic traits）上存在差异（例如生理学特征、行为模式等），但这些差异究竟是固定不变的，还是由外部环境条件驱动的，目前仍尚不明确。我们以斑姬鹟（collared flycatchers）为研究对象，通过在育雏期（nestling rearing period）补充额外食物，实验检验了扩散个体与非扩散个体间的巢防御行为（nest-defence behaviour）差异是否随局部生境质量（local habitat quality）发生变化。在未补充食物的对照巢中，扩散个体相较于非扩散个体更不易开展巢防御行为；而在补充食物的巢中，两类个体则表现出强度相当的巢防御行为。我们探讨了扩散成本（dispersal costs）与繁殖投入（reproductive investment）的适应性可塑性（adaptive flexibility）在塑造扩散个体与非扩散个体间巢防御行为差异中的重要作用。无论潜在机制如何，本研究均强调，在比较扩散个体与非扩散个体间的性状差异时，需纳入环境效应的考量，进而评估扩散行为的成本与收益。