Experimental harvest regulations reveal that water availability during spring, not harvest, affects change in a waterfowl population

Population change is regulated by vital rates that are influenced by environmental conditions, demographic stochasticity and increasingly, anthropogenic effects. Habitat destruction and climate change threaten the future of many wildlife populations, and there are additional concerns regarding the effects of harvest rates on demographic components of harvested organisms. Further, many population managers strictly manage harvest of wild organisms to mediate population trends of these populations. The goal of our study was to decouple harvest and environmental variability in a closely monitored population of wild ducks in North America, where we experimentally regulated harvest independently of environmental variation over a period of four years. We used nine years of capture-mark-recapture data to estimate breeding population size during the spring for a population of wood ducks in Nevada. We then assessed the effect of one environmental variable and harvest pressure on annual changes...种群动态变化由生命率调控，而生命率受到环境条件、种群统计随机性（demographic stochasticity）以及日益凸显的人为活动影响。栖息地破坏与气候变化正威胁着诸多野生动物种群的存续，此外，人们还担忧捕获率对被捕获物种的种群统计特征所产生的影响。进一步而言，众多种群管理者会对野生生物的捕获活动实施严格管控，以调节此类种群的动态趋势。本研究的目标为：在北美一处被严密监测的野生鸭类种群中，剥离捕获效应与环境变异的相互影响；我们在四年的周期内，通过实验手段在不受环境变化干扰的前提下调控捕获强度。我们利用内华达州林鸭（wood duck）种群九年的标记重捕（capture-mark-recapture）数据，估算了该种群春季的繁殖种群规模。随后，我们评估了单种环境变量与捕获压力对种群年度变化的影响……