Data from: Individual variation in winter supplementary food consumption and its consequences for reproduction in wild birds.

The provision of wild birds with supplementary food has increased substantially over recent decades. While it is assumed that provisioning birds is beneficial, supplementary feeding can have detrimental ‘carry-over’ effects on reproductive traits. Due to difficulties in monitoring individual feeding behaviour, assessing how individuals within a population vary in their exploitation of supplementary food resources has been limited. Quantifying individual consumption of supplementary food is necessary to understand the operation of carry-over effects at the individual level. We used Radio Frequency Identification (RFID) technology and automated feeders to estimate individual consumption of supplementary winter food in a large wild population of great tits Parus major and blue tits Cyanistes caeruleus. Using these data, we identified demographic factors that explained individual variation in levels of supplementary food consumption. We also tested for carry-over effects of supplementary food consumption on recruitment, reproductive success and a measure of survival. Individual variation in consumption of supplementary food was explained by differences between species, ages, sexes and years. Individuals were consistent across time in their usage of supplementary resources. We found no strong evidence that the extent of supplementary food consumption directly influenced subsequent fitness parameters. Such effects may instead result from supplementary food influencing population demographics by enhancing the survival and subsequent breeding of less competitive individuals, which reduce average breeding parameters and increase density-dependent competition. Carry-over effects of supplementary feeding are not universal and may depend upon the temporal availability of the food provided. Our study demonstrates how RFID systems can be used to examine individual-level behaviour with minimal effects on fitness.

近数十年来，为野生鸟类提供补充食物的行为已显著增多。尽管普遍认为人工投喂对鸟类有益，但补充投喂可能会对繁殖性状产生有害的遗留效应（carry-over effects）。由于难以监测个体的取食行为，评估种群内个体对补充食物资源的利用差异始终面临局限。量化个体对补充食物的消耗量，是解析个体层面遗留效应运作机制的必要前提。我们借助射频识别（Radio Frequency Identification, RFID）技术与自动喂食器，对大山雀（Parus major）和蓝山雀（Cyanistes caeruleus）这两个大型野生种群的冬季补充食物个体消耗量进行了估算。基于这些数据，我们阐明了能够解释补充食物消耗水平个体差异的种群统计因素，同时检验了补充食物消耗对种群招募、繁殖成效以及生存状况指标的遗留效应。个体在补充食物的消耗上存在的差异可由物种、年龄、性别以及年份之间的差异来解释，且个体对补充资源的利用在时间维度上具有一致性。我们未发现强有力的证据表明，补充食物的消耗程度会直接影响后续的适合度参数。此类效应或许反而源于补充食物通过提升竞争力较弱个体的存活率与后续繁殖能力，进而影响种群统计特征：这一过程会降低平均繁殖参数，并加剧密度依赖型竞争。补充投喂的遗留效应并非普遍存在，其发生可能取决于所提供食物的时间维度可获得性。本研究证明，RFID系统可在对个体适合度影响极小的前提下，用于开展个体水平的行为研究。