Data from: Supplementary winter feeding is associated with higher recruitment rates in a population of a scavenging bird of prey

Supplementary feeding is a widely used conservation strategy to support scavenging species, but the full effects remain poorly understood. In the Baltic Sea region, the recovery of the white-tailed eagle (Haliaeetus albicilla) was assisted by an extensive feeding scheme. We examined whether the individual usage of a feeder was associated with the probability to recruit into the local population. At a feeder in Southwest Finland, food was offered during winter and visiting individuals were identified based on their unique ring codes. Additionally, we identified individuals by genotypes extracted from feathers collected from ringed nestlings and from adult feathers collected from nests between 2003-2012 and 2008-2023, respectively. By matching nestling and adult genotypes, we infer recruitment and relate it to feeder usage. In addition, we explore sex-specific differences, which could arise due to intra-specific competition due to size differences. Our findings reveal that there was high individual variability in feeder usage and that visitation rate was positively associated with the probability to recruit. Although females spent more time at the feeder, recruitment was irrespective of sex. While for individuals the probability to recruit increased from 13.6% to 43.0%, the population-level increases were small, from 13.6% to 14.7%. We demonstrate that winter feeding had the potential to aid the recovery of the white-tailed eagle in the region, although estimating the full effect of supplementary food for the population would require further analyses. Our study highlights the consequences of supplementary feeding and facilitates more informed management strategies for conservation of endangered species.

补充投喂（Supplementary feeding）是广泛应用于食腐物种种群保护的保育策略，但其完整生态效应仍未被充分阐明。在波罗的海海域，白尾海雕（Haliaeetus albicilla）的种群恢复曾得益于一项大规模投喂计划。本研究旨在探究个体对投喂点的使用情况是否与该个体加入当地繁殖种群的招募概率存在关联。在芬兰西南部的一处投喂点，研究人员于冬季提供食物，并通过个体独有的环志编码识别到访的白尾海雕。此外，研究人员分别通过2003-2012年采集的环志雏鸟羽毛、以及2008-2023年采集的成鸟巢羽中提取的基因型，对个体进行识别。通过比对雏鸟与成鸟的基因型，研究人员可推断个体的招募情况，并将其与投喂点到访行为相关联。此外，本研究还探讨了性别的特异性差异——这类差异可能源于体型差异引发的种内竞争。研究结果显示，个体在投喂点的使用行为存在显著的个体差异，且到访频次与种群招募概率呈正相关关系。尽管雌性白尾海雕在投喂点停留的时间更长，但种群招募概率并不受性别影响。就个体层面而言，招募概率从13.6%提升至43.0%；但种群层面的增幅却较为有限，仅从13.6%升至14.7%。本研究证实，冬季投喂有助于推动该区域白尾海雕的种群恢复，不过若要量化补充投喂对种群的完整效应，还需开展进一步的分析研究。本研究揭示了补充投喂的生态后果，可为濒危物种的保护管理策略制定提供更科学的参考依据。