Data from: Comparative demographics of a Hawaiian forest bird community

Estimates of demographic parameters such as survival and reproductive success are critical for guiding management efforts focused on species of conservation concern. Unfortunately, reliable demographic parameters are difficult to obtain for any species, but especially for rare or endangered species. Here we derived estimates of adult survival and recruitment in a community of Hawaiian forest birds, including eight native species (of which three are endangered) and two introduced species at Hakalau Forest National Wildlife Refuge, Hawaiʻi. Integrated population models (IPM) were used to link mark-recapture data (1994-1999) with long-term population surveys (1987-2008). To our knowledge, this is the first time that IPM have been used to characterize demographic parameters of a whole avian community, and provides important insights into the life history strategies of the community. The demographic data were used to test two hypotheses: (i) arthropod specialists, such as the ‘Akiapōlā‘au (Hemignathus munroi), are 'slower' species characterized by a greater relative contribution of adult survival to population growth, i.e. lower fecundity and increased adult survival; and (ii) a species’ susceptibility to environmental change, as reflected by its conservation status, can be predicted by its life history traits. We found that all species were characterized by a similar population growth rate around one, independently of conservation status, origin (native vs. non-native), feeding guild, or life history strategy (as measured by 'slowness'), which suggested that the community had reached an equilibrium. However, such stable dynamics were achieved differently across feeding guilds, as demonstrated by a significant increase of adult survival and a significant decrease of recruitment along a gradient of increased insectivory, in support of hypothesis (i). Supporting our second hypothesis, we found that slower species were more vulnerable species at the global scale than faster ones. The possible causes and conservation implications of these patterns are discussed.

诸如存活率与繁殖成功率等种群统计参数（demographic parameters）的估算，对于指导受保护物种的管理工作至关重要。然而，无论对于何种物种，获取可靠的种群统计参数都颇具难度，珍稀或濒危物种更是如此。本研究于夏威夷哈卡拉森林国家野生动物保护区，针对夏威夷森林鸟类群落开展了成体存活率与种群补充量（recruitment）的估算，该群落包含8个本土鸟类物种（其中3种为濒危物种）与2个外来物种。研究采用整合种群模型（Integrated Population Models, IPM），将标记重捕数据（mark-recapture data，1994-1999年）与长期种群调查数据（1987-2008年）进行关联分析。据我们所知，本研究首次将整合种群模型应用于完整鸟类群落的种群统计参数刻画，为该群落的生活史策略（life history strategy）研究提供了重要见解。本研究利用种群统计数据检验了两项假说：其一，节肢动物专食者（arthropod specialists，如‘Akiapōlā‘au（Hemignathus munroi））属于‘慢生活史’物种，其成体存活率对种群增长的相对贡献更高，即繁殖力（fecundity）较低而成体存活率更高；其二，物种对环境变化的敏感性可通过其保护等级体现，且可通过其生活史特征进行预测。研究发现，所有物种的种群增长率均接近1，不受保护等级、起源（本土 vs 外来）、取食功能群（feeding guild）或生活史策略（以‘慢生活史’程度衡量）的影响，表明该群落已达到平衡状态。不过，不同取食功能群实现稳定种群动态的路径存在差异：随着食虫性（insectivory）程度升高，成体存活率显著提升而种群补充量显著下降，这一结果支持了第一项假说。同时，研究结果支持第二项假说：在全球尺度上，慢生活史物种比快生活史物种更易受到威胁。本研究最后探讨了上述格局的潜在成因及其保护意义。