Manuscript_redkite_migcon_data_codes

Abstract Migratory connectivity, the linkage between breeding and non-breeding populations, is crucial for understanding the ecology and conservation of migratory species across their range. Differential migration, where subgroups within a population have varying migratory strategies (e.g. different migration flyways), is common in many vertebrate species and predicted to affect migratory connectivity. However, empirical evidence for this prediction is largely lacking due to logistical and financial constraints. Here, we examine the impact of differential migration on the range-wide migratory network and migratory connectivity of the red kite (Milvus milvus) using an unprecedented GPS tracking dataset of 2,440 annual cycles from 1,020 individuals, along with range-wide breeding abundance maps. Our analysis reveals significant spatial variation in age-dependent residency and flyways, creating a mosaic of differential migration across the species’ range. Unlike adults and immature birds, juveniles show more spatial variation in migration strategy, with 21.3% of the global juvenile population and 43.6% of the adults remaining resident year-round. We identified a clear migratory divide, with 77.7% of all juveniles and 54.0% of adults adopting a western flyway, and 68% of the global juvenile and 56% of the adult population overwintering on the Iberian Peninsula. Combining transition probabilities with abundance estimates indicated weak, but age-structured migratory connectivity, with migratory connectivity (MC) values decreasing from 0.34 in juveniles to 0.27 in adults. As higher values indicate greater separation and less mixing on the wintering grounds, our results suggest that adults from different breeding populations mix more extensively than juveniles, highlighting an age-related diversification of migration patterns. These findings highlight the need for tailored management strategies that account for age-specific migration patterns and their geographic variation. Our study provides the first empirical evidence that age-structured differential migration causes age-specific migratory connectivity across a vertebrate’s entire range, with important implications for conservation and population management.摘要 迁徙连通性（migratory connectivity）指繁殖种群与非繁殖种群之间的关联，对于理解迁徙物种在其分布范围内的生态学特征与保护策略至关重要。差异迁徙（differential migration）指种群内不同亚群具有各异的迁徙策略（例如不同的迁徙通道），这一现象在众多脊椎动物物种中普遍存在，且被预测会对迁徙连通性产生影响。然而，受后勤与经费限制，相关预测的实证证据目前仍较为匮乏。 本研究基于覆盖1020只个体、共计2440个年度周期的空前规模GPS追踪数据集（GPS tracking dataset），结合全分布范围的繁殖丰度分布图，探究了差异迁徙对红鸢（Milvus milvus）全分布范围迁徙网络及迁徙连通性的影响。 分析结果显示，基于年龄的居留策略与迁徙通道存在显著空间变异，在该物种的分布范围内形成了差异迁徙的镶嵌格局。与成鸟和亚成鸟不同，幼鸟的迁徙策略空间变异更为显著：全球范围内21.3%的幼鸟与43.6%的成鸟全年居留于固定区域。研究明确识别出一条清晰的迁徙分界带：77.7%的幼鸟与54.0%的成鸟采用西部迁徙通道，且全球68%的幼鸟、56%的成鸟在伊比利亚半岛越冬。结合转移概率与丰度估算值的分析结果表明，迁徙连通性存在微弱但受年龄结构调控的特征，迁徙连通性（MC）值从幼鸟的0.34下降至成鸟的0.27。由于更高的MC值意味着越冬地的种群分离程度更高、混合程度更低，本研究结果显示，不同繁殖种群的成鸟比幼鸟的混合程度更高，这凸显了迁徙模式随年龄产生的分化。 上述研究结果凸显了制定针对性管理策略的必要性，需充分考虑年龄特异性的迁徙模式及其地理变异。本研究首次提供实证证据，证明受年龄结构调控的差异迁徙会导致脊椎动物全分布范围内出现年龄特异性的迁徙连通性，这一发现对物种保护与种群管理具有重要意义。