Vertebrate Zoology Department, MUSE - Science Museum, Corso del Lavoro e della Scienza 3, 38122, Trento, TN, Italy.
Research and Innovation Centre, Fondazione Edmund Mach, via E. Mach 1, 38010, San Michele all'Adige, Italy.
Sci Rep. 2021 Oct 21;11(1):20800. doi: 10.1038/s41598-021-00373-9.
Naturally occurring stable isotope ratios in animal tissues allow estimation of species trophic position and ecological niche. Measuring multiple isotopes of migratory species along flyway bottlenecks offers the opportunity to sample multiple populations and species whose tissues carry information at continental scales. We measured δH, δO, δC, δN in juvenile feathers of 21 bird species captured at a migratory bottleneck in the Italian Alps. We examined if trends in individual isotopes reflected known migratory strategies and whether dietary (δC-δN) and spatially-explicit breeding origin (δH-δO) niche breadth (NB) differed among long-distance trans-Saharan (TS), short-distance (IP) and irruptive (IR) intra-Palearctic migrants, and whether they correlated with reported populations long-term trends. In both TS and IP groups, species δH declined with capture date, indicating that northern populations reached the stopover site later in the season, following a Type-I migration strategy. Values of δH indicated that breeding range of TS migrants extended farther north than IP and IR migrants. The breeding season was longer for IP migrants whose δC and δN values declined and increased, respectively, with time of capture. Average species dietary NB did not differ among migratory groups, but TS migrants displayed wider breeding origin niches, suggesting that long-distant migration is linked to broader ecological niches. Isotope origin NB well reflected species geographic range extent, while dietary NB did not correlate with literature accounts of species' diet. We found no relationship between species breeding NB and population trends in Europe, suggesting that conditions in the breeding grounds, as inferred by stable isotopes, are not the only determinant of species' long-term persistence. We demonstrate that ringing activities and isotopic measurements of passerines migrating through a bottleneck represents a unique opportunity to investigate large-scale life-history phenomena relevant to conservation.
动物组织中天然存在的稳定同位素比值可用于估计物种的营养位置和生态位。在迁徙物种的飞行路线瓶颈处测量多种同位素，为采样具有大陆尺度信息的多个种群和物种提供了机会。我们测量了在意大利阿尔卑斯山迁徙瓶颈处捕获的 21 种鸟类幼鸟的 δH、δO、δC 和 δN。我们研究了个体同位素的趋势是否反映了已知的迁徙策略，以及饮食（δC-δN）和空间明确的繁殖起源（δH-δO）的生态位宽度（NB）是否在长距离跨撒哈拉（TS）、短距离（IP）和爆发性（IR）内部迁徙者之间存在差异，以及它们是否与报道的种群长期趋势相关。在 TS 和 IP 组中，随着捕获日期的推移，物种 δH 呈下降趋势，表明北方种群在季节后期到达中途停留地，遵循 I 型迁徙策略。TS 迁徙者的 δH 值表明，它们的繁殖范围比 IP 和 IR 迁徙者向北延伸更远。IP 迁徙者的繁殖季节更长，其 δC 和 δN 值分别随着捕获时间的推移而下降和增加。迁徙群体之间的平均物种饮食 NB 没有差异，但 TS 迁徙者的繁殖起源生态位更宽，这表明远距离迁徙与更广泛的生态位相关。同位素起源 NB 很好地反映了物种的地理范围，而饮食 NB 与物种饮食的文献报道没有相关性。我们发现物种繁殖 NB 与欧洲物种的种群趋势之间没有关系，这表明稳定同位素推断的繁殖地条件不是物种长期生存的唯一决定因素。我们证明，通过瓶颈处迁徙的雀形目鸟类的环志活动和同位素测量为研究与保护相关的大规模生活史现象提供了独特的机会。
