Data from: Long-term population dynamics reveal that survival and recruitment of tropical boobies improve after a hurricane

Variability in population numbers is a central issue in evolutionary ecology and also in biodiversity conservation. However, for most seabirds this information is lacking and tropical populations are virtually unstudied. Long-term studies are warranted because world’s seabird populations exhibit an overall declining trend since 1950. Using data spanning 23 years, we investigated how adult survival, local recruitment, and their relative contributions to population growth (λ) vary over time in the blue-footed booby (Sula nebouxii), a long-lived locally foraging seabird that breeds in tropical waters. In addition, we investigated whether booby demographic rates exhibit the same declining trend observed in other seabirds, whether these rates are impacted by hurricanes, and whether these potential impacts differ between sexes. Our analysis of 4608 capture-recapture histories revealed that survival and recruitment were nearly equal between males and females, exhibited a declining trend over the last 23 years, and in both sexes, these vital rates improved after a hurricane. The declining trend in recruitment was slightly more attenuated in males. These results add to the current evidence for an overall declining trend in world’s seabird populations and extend its confirmation to the warm eastern tropical Pacific. Moreover, they provide the first evidence that hurricanes may favor natural populations. As a result of the declining trend and variation in survival and recruitment, λ exhibited a slight decline and substantial variation over the 23 years. However, most λ values were equal to or higher than 1, and the long-term average indicates population increase. The ability of blue-footed boobies to maintain a positive population balance despite of negative trends in their vital rates might result from canalization of adult survival (the vital rate that contributes most to λ and shows lower variation compared to recruitment) against environmental variability.

种群数量动态变化是进化生态学与生物多样性保护领域的核心议题之一。然而，绝大多数海鸟的相关数据仍存在缺失，热带海鸟种群更是几乎未被深入研究。鉴于全球海鸟种群自1950年以来整体呈下降趋势，开展长期研究实属必要。本研究依托跨度23年的调查数据，以在热带水域繁殖的长寿命本地觅食海鸟——蓝脚鲣鸟（Sula nebouxii）为研究对象，探讨了其成体存活率、本地种群补充率及其对种群增长（λ）的相对贡献随时间的变化规律。
此外，本研究还探讨了三个核心科学问题：蓝脚鲣鸟的种群统计参数是否呈现与其他海鸟一致的下降趋势？这些参数是否会受到飓风的影响？且这类潜在影响是否存在性别差异？
通过对4608份捕获-再捕获（capture-recapture）记录的分析，我们发现：雌雄个体的成体存活率与种群补充率基本持平；在过去23年间，这两项参数均呈下降趋势；且无论雌雄，飓风过后这两项关键生活史参数均有所改善。雄性个体的种群补充率下降趋势略弱于雌性。
本研究结果进一步佐证了全球海鸟种群整体下降的现状，并将该结论的验证范围拓展至东太平洋暖水海域。此外，本研究还首次提供了飓风可能对自然种群产生正向影响的证据。
受成体存活率与种群补充率的下降趋势及波动影响，种群增长参数λ在23年的研究周期内呈现小幅下降与显著波动。但绝大多数λ值均大于或等于1，长期平均λ值表明该种群整体呈增长态势。
尽管自身关键生活史参数呈负向趋势，蓝脚鲣鸟仍能维持种群正向平衡，这一能力可能源于成体存活率对环境波动的发育缓冲作用——成体存活率是对种群增长贡献最大的参数，且相较于种群补充率，其波动幅度更低。