Scholarlink

<p>Stopover sites play a key role in migratory bird ecology, yet estimating abundance at these sites is challenging, because migration is temporally heterogeneous and sampling can be incomplete. Robust abundance indices are crucial for long-term monitoring and comparative analyses across years and sites. Using 18 years of constant-effort mist-netting data from a major stopover site in northern Spain, this study aimed to evaluate whether simple abundance indices can reliably track more complex model-based estimates. The performance of the mean number of captures per day (MCD) and means above percentile-based indices (A80, A90) with abundance estimates derived from Generalized Additive Models (by assessing the area under the curve, AUC) was compared. In addition, simulation analyses were conducted to evaluate the robustness of these indices under different phenological patterns, abundance levels, and sampling coverage. Across species and age classes, simpler indices (particularly MCD) were highly correlated with GAM-derived AUC estimates, indicating that they effectively captured interannual variation in stopover use. In contrast, those indices based on extreme values (A90) showed weaker and more variable relationships, especially for less abundant groups, reflecting sensitivity to stochastic events. Overall, results suggest that simpler metrics such as MCD provide robust, transparent, and cost-effective abundance estimates, which might support their use in long-term and large-scale monitoring programs.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Simplifying complexity: toward alternative robust stopover abundance indices for migratory landbirds

  • 期刊论文

  • 发表日期：

    2026年4月20日

查看全文
  • Juan Arizaga

摘要

Stopover sites play a key role in migratory bird ecology, yet estimating abundance at these sites is challenging, because migration is temporally heterogeneous and sampling can be incomplete. Robust abundance indices are crucial for long-term monitoring and comparative analyses across years and sites. Using 18 years of constant-effort mist-netting data from a major stopover site in northern Spain, this study aimed to evaluate whether simple abundance indices can reliably track more complex model-based estimates. The performance of the mean number of captures per day (MCD) and means above percentile-based indices (A80, A90) with abundance estimates derived from Generalized Additive Models (by assessing the area under the curve, AUC) was compared. In addition, simulation analyses were conducted to evaluate the robustness of these indices under different phenological patterns, abundance levels, and sampling coverage. Across species and age classes, simpler indices (particularly MCD) were highly correlated with GAM-derived AUC estimates, indicating that they effectively captured interannual variation in stopover use. In contrast, those indices based on extreme values (A90) showed weaker and more variable relationships, especially for less abundant groups, reflecting sensitivity to stochastic events. Overall, results suggest that simpler metrics such as MCD provide robust, transparent, and cost-effective abundance estimates, which might support their use in long-term and large-scale monitoring programs.