Estimating transient populations of unmarked individuals at a migratory stopover site using generalized N-mixture models

1. Migration counts are popular indices used to monitor population trends over time. Advanced analytical methods for estimating abundance of unmarked, open populations now incorporate population growth models and simultaneously test for covariate effects on abundance and detection probability. However, estimating population abundance at a staging site is complicated by daily immigration and emigration of unmarked individuals. 2. We applied a set of generalized N-mixture models to simulated count data to test their applicability for transient populations. Using simulated datasets, parameters were unbiased when the apparent survival rate varied within a season or was mis-specified in a model, but not when the immigration or detection probability was mis-specified. 3. With knowledge from the simulated data, we applied these models to daily counts of staging migratory shorebirds and estimated daily abundances accounting for variation in the detection and immigration rates. Daily counts of ...1. 迁徙计数是长期监测种群动态的常用指标。当前用于估算无标记开放种群丰度的高级分析方法，已整合种群增长模型，并可同时检验协变量对丰度与检测概率的影响。然而，在停歇位点估算种群丰度时，会因无标记个体每日的迁入与迁出而变得复杂。 2. 我们将一系列广义N-mixture模型（generalized N-mixture models）应用于模拟计数数据，以检验其在迁移过境种群中的适用性。基于模拟数据集的结果显示：当表观存活率在季内发生变化，或模型中对其设定有误时，参数估计无偏；但当迁入率或检测概率的模型设定有误时，参数估计则存在偏差。 3. 基于模拟数据得到的先验知识，我们将上述模型应用于迁徙滨鸟停歇地的每日计数数据，估算了考虑检测率与迁入率变异的每日种群丰度。每日计数……