Seabirds, being long-lived top-level marine predators, are often considered to be valuable environmental indicators. With growing evidence of seabird declines worldwide, it is essential to monitor changes in populations and determine drivers of change. The Seychelles Archipelago supports the greatest abundance of seabirds in the tropical Indian Ocean, but regional seabird population breeding success and trend data are not readily available despite multi-year data collection at several locations. Here we use monitoring data on White-tailed Tropicbirds (Phaethon lepturus) in the Seychelles to present the first nation-wide assessment of the status and trends of breeding success at five key sites. Mean annual breeding success was 15% for Aldabra Atoll in the southern Seychelles and 33–55% in the inner islands (Aride, Cousine, Denis, and Cousin). In the inner islands there are indications of potential population declines (inferred from declining nesting activity rates at Aride), despite stable and comparatively high breeding success. This contrasts with Aldabra where nesting activity has been relatively stable, but a decline in breeding success is causing concern. Our study highlights clear priorities for management of P. lepturus populations in the Seychelles; the causes of the declines in P. lepturus breeding population at Aride and breeding success at Aldabra should be a focus of future research and monitoring. We propose the adoption of standardized monitoring programs and increased site coverage across the Seychelles and the broader Western Indian Ocean. This, coupled with increased pooling of data and regular analysis, will strengthen the collective effort toward the conservation management of this and other seabird species within this global seabird hotspot.

中文翻译：

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结合多个地点的监测数据，评估塞舌尔白尾热带鸟（Phaethon lepturus）的种群状况和趋势

海鸟是长寿的顶级海洋捕食者，通常被认为是有价值的环境指标。随着世界范围内海鸟数量减少的证据越来越多，监测种群变化并确定变化的驱动因素至关重要。塞舌尔群岛支持热带印度洋中最丰富的海鸟，但尽管在多个地点收集了多年数据，但仍无法获得区域海鸟种群繁殖成功和趋势数据。在这里，我们使用塞舌尔白尾热带鸟 (Phaethon lepturus) 的监测数据，对五个关键地点的繁殖成功状况和趋势进行了首次全国性评估。塞舌尔南部阿尔达布拉环礁的平均年繁殖成功率为 15%，内岛（Aride、Cousine、Denis 和 Cousin）为 33-55%。在内岛，尽管繁殖成功率稳定且相对较高，但仍有潜在种群下降的迹象（从 Aride 的筑巢活动率下降推断）。这与阿尔达布拉形成鲜明对比，阿尔达布拉的筑巢活动相对稳定，但繁殖成功率的下降令人担忧。我们的研究强调了管理塞舌尔 P. lepturus 种群的明确优先事项；Aride 的 P. lepturus 繁殖种群下降的原因和 Aldabra 的繁殖成功应该是未来研究和监测的重点。我们建议在塞舌尔和更广泛的西印度洋采用标准化监测计划并增加站点覆盖范围。再加上增加的数据汇集和定期分析，