Globally, anthropogenic land-cover change has been dramatic over the last few centuries and is frequently invoked as a major cause of wildlife population declines. Baseline data currently used to assess population trends, however, began well after major changes to the landscape. In the United States and Canada, breeding bird population trends are assessed by the North American Breeding Bird Survey, which began in the 1960s. Estimates of distribution and abundance prior to major habitat alteration would add historical perspective to contemporary trends and allow for historically based conservation targets. We used a hindcasting framework to estimate change in distribution and abundance of 7 bird species in the Willamette Valley, Oregon (United States). After reconciling classification schemes of current and 1850s reconstructed land cover, we used multiscale species distribution models and hierarchical distance sampling models to predict spatially explicit densities in the modern and historical landscapes. We estimated that since the 1850s, White-breasted Nuthatch (Sitta carolinensis) and Western Meadowlark (Sturnella neglecta) populations, 2 species sensitive to fragmentation of oak woodlands and grasslands, declined by 93% and 97%, respectively. Five other species we estimated nearly stable or increasing populations, despite steep regional declines since the 1960s. Based on these estimates, we developed historically based conservation targets for amount of habitat, population, and density for each species. Hindcasted reconstructions provide historical perspective for assessing contemporary trends and allow for historically based conservation targets that can inform current management.

中文翻译：

---

建立更好的基线来估计 160 年的鸟类种群变化并制定历史知情保护目标

在全球范围内，过去几个世纪以来，人为造成的土地覆盖变化非常剧烈，并且经常被认为是野生动物数量下降的主要原因。然而，目前用于评估人口趋势的基线数据是在景观发生重大变化之后才开始的。在美国和加拿大，繁殖鸟类种群趋势由 1960 年代开始的北美繁殖鸟类调查进行评估。在主要栖息地改变之前对分布和丰度的估计将为当代趋势增加历史视角，并允许基于历史的保护目标。我们使用后报框架来估计美国俄勒冈州威拉米特河谷 7 种鸟类的分布和丰度变化。在协调当前和 1850 年代重建土地覆盖的分类方案后，我们使用多尺度物种分布模型和分层距离采样模型来预测现代和历史景观中的空间显性密度。我们估计，自 1850 年代以来，对橡树林地和草地破碎化敏感的 2 种白胸鹬 (Sitta carolinensis) 和西部草地鹨 (Sturnella ignorea) 种群分别下降了 93% 和 97%。尽管自 1960 年代以来区域急剧下降，但我们估计其他五个物种的种群数量几乎稳定或增加。根据这些估计，我们针对每个物种的栖息地数量、人口数量和密度制定了基于历史的保护目标。