Population models used in: Method to assess potential magnitude of terrestrial European avian population reductions from ingestion of lead ammunition

Current estimates of terrestrial bird losses across Europe from ingestion of lead ammunition are based on uncertain or generic assumptions. A method is needed to develop defensible European-specific estimates compatible with available data that does not require long-term field studies. We propose a 2-step method using carcass data and population models. The method estimates percentage of deaths diagnosed as directly caused by lead poisoning as a lower bound and, as an upper bound, the percentage of possible deaths from sublethal lead poisoning that weakens birds, making them susceptible to death by other causes. We use these estimates to modify known population-level annual mortality. Our method also allows for potential reductions in reproduction from lead shot ingestion because reductions in survival and reproduction are entered into population models of species with life histories representative of the most groups of susceptible species. The models estimate the sustainability and potential population decreases from lead poisoning in Europe. Using the best available data, we demonstrate the method on two taxonomic groups of birds: gallinaceous birds and diurnal raptors. The direction of the population trends affects the estimate, and we incorporated such trends into the method. Our midpoint estimates of the reduction in population size of the European gallinaceous bird (< 2%) group and raptor group (2.9 – 7.7%) depend on the species life history, maximum growth rate, population trend, and if reproduction is assumed to be reduced. Our estimates can be refined as more information becomes available in countries with data gaps. We advocate use of this method to improve upon or supplement approaches currently being used. As we demonstrate, the method also can be applied to individual species of concern if enough data across countries are available.

当前针对欧洲陆地鸟类因摄入铅弹药（lead ammunition）导致的死亡量估算，均基于不确定或通用化的假设前提。亟需开发一种适配现有数据、无需开展长期野外研究的可信欧洲专属估算方法。本研究提出一种两步法，结合尸体数据（carcass data）与种群模型（population models）开展相关估算：该方法将经诊断由铅中毒（lead poisoning）直接致死的死亡占比作为估算下限，同时将亚致死铅中毒（sublethal lead poisoning）导致鸟类体质衰弱、进而易因其他诱因死亡的潜在死亡占比作为估算上限。我们利用上述估算结果修正已有的种群水平年死亡率数据。本方法同时可考量铅弹摄入对繁殖成功率的潜在负面影响：我们将存活率与繁殖率的下降参数，代入具有典型易感鸟类类群生活史（life histories）特征的物种种群模型中。这些模型可评估欧洲地区铅中毒对鸟类种群的可持续性影响及其潜在种群下降幅度。我们基于现有最优数据，以鸡形目鸟类（gallinaceous birds）与昼行性猛禽（diurnal raptors）这两个鸟类分类类群为例，验证了该方法的可行性。种群趋势的方向会对估算结果产生影响，因此我们将种群趋势纳入该方法体系中。欧洲鸡形目鸟类种群规模降幅的中点估算值低于2%，昼行性猛禽的降幅中点估算值为2.9%至7.7%；该结果取决于物种生活史特征、最大增长率、种群趋势以及是否假设繁殖率下降。针对存在数据缺口的国家，随着更多相关信息的补充，我们的估算结果可进一步优化完善。我们倡议采用该方法，对当前已有的相关研究方法进行改进或补充。如本研究所示，若能获取跨国家的充足数据，该方法也可应用于受关注的单个物种。