Abstract Context. The ring-necked pheasant (Phasianus colchicus) has experienced considerable population declines in recent decades, especially in agricultural environments of the Central Valley of California. Although large-scale changes in land cover have been reported as an important driver of population dynamics, the effects of microhabitat conditions on specific demographic rates (e.g. nesting) are largely unknown. Aims. Our goal was to identify the key microhabitat factors that contribute to wild pheasant fitness by linking individual-level selection of each microhabitat characteristic to the survival of their nests within the California Central Valley. Methods. We radio- or GPS-marked 190 female ring-necked pheasants within five study areas and measured nest-site characteristics and nest fates during 2013–2017. Specifically, we modeled microhabitat selection using vegetation covariates measured at nest sites and random sites and then modeled nest survival as a function of selecting each microhabitat characteristic. Key results. Female pheasants tended to select nest sites with greater proportions of herbaceous cover and avoided areas with greater proportions of bare-ground. Specifically, perennial grass cover was the most explanatory factor with regard to nest survival, but selection for increasing visual obstruction alone was not shown to have a significant effect on survival. Further, we found strong evidence that pheasants selecting sites with greater perennial grass height were more likely to have successful nests. Conclusions. Although pheasants will select many types of vegetation available as cover, our models provided evidence that perennial grasses are more beneficial than other cover types to pheasants selecting nesting sites. Implications. Focusing management actions on promoting perennial grass cover and increased heights at the microsite level, in lieu of other vegetative modifications, may provide improved quality of habitat for nesting pheasants and, perhaps, result in increased productivity. This is especially important if cover is limited during specific times of the nesting period. Understanding how microhabitat selection influences fitness can help land managers develop strategies to increase the sustainability of hunted populations of this popular game-bird species.

中文翻译：

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将巢穴微生境选择与加利福尼亚中央谷野鸡种群数量下降的巢穴生存联系起来

摘要上下文。近几十年来，环颈雉（Phasianus colchicus）的种群数量大幅下降，尤其是在加利福尼亚中央山谷的农业环境中。尽管据报道土地覆盖的大规模变化是人口动态的重要驱动因素，但微生境条件对特定人口比率（例如筑巢）的影响在很大程度上是未知的。目标。我们的目标是通过将每个微生境特征的个体水平选择与加利福尼亚中央山谷内巢穴的生存联系起来，确定有助于野雉健康的关键微生境因素。方法。我们在 2013-2017 年期间对五个研究区域内的 190 只雌性环颈雉进行了无线电或 GPS 标记，并测量了巢址特征和巢穴命运。具体来说，我们使用在巢址和随机地点测量的植被协变量对微生境选择进行建模，然后将巢穴生存建模为选择每个微生境特征的函数。关键结果。雌性雉鸡倾向于选择草本覆盖率更高的筑巢地点，并避开裸地比例更大的地区。具体而言，多年生草覆盖是关于巢穴存活的最能解释因素，但仅选择增加视觉障碍的选择并未显示对存活有显着影响。此外，我们发现强有力的证据表明，选择多年生草高较高的地点的野鸡更有可能成功筑巢。结论。虽然野鸡会选择多种可用的植被作为掩护，我们的模型提供的证据表明，多年生草比其他覆盖类型对选择筑巢地点的野鸡更有利。影响。将管理行动的重点放在促进多年生草覆盖和增加微型场地级别的高度上，而不是其他植被改造，可能会改善筑巢野鸡的栖息地质量，并可能提高生产力。如果在筑巢期间的特定时间覆盖有限，这一点尤其重要。了解微生境选择如何影响健康可以帮助土地管理者制定战略，以提高这种流行的猎鸟物种的狩猎种群的可持续性。将管理行动的重点放在促进多年生草覆盖和增加微型场地级别的高度上，而不是其他植被改造，可能会改善筑巢野鸡的栖息地质量，并可能提高生产力。如果在筑巢期间的特定时间覆盖有限，这一点尤其重要。了解微生境选择如何影响健康可以帮助土地管理者制定战略，以提高这种流行的猎鸟物种的狩猎种群的可持续性。将管理行动的重点放在促进多年生草覆盖和增加微型场地级别的高度上，而不是其他植被改造，可能会改善筑巢野鸡的栖息地质量，并可能提高生产力。如果在筑巢期间的特定时间覆盖有限，这一点尤其重要。了解微生境选择如何影响健康可以帮助土地管理者制定战略，以提高这种流行的猎鸟物种的狩猎种群的可持续性。