Passive acoustic monitoring using autonomous recording units (ARUs) is a fast-growing area of wildlife research especially for rare, cryptic species that vocalize. Northern Spotted Owl (Strix occidentalis caurina) populations have been monitored since the mid-1980s using mark–recapture methods. To evaluate an alternative survey method, we used ARUs to detect calls of Northern Spotted Owls and Barred Owls (S. varia), a congener that has expanded its range into the Pacific Northwest and threatens Northern Spotted Owl persistence. We set ARUs at 30 500-ha hexagons (150 ARU stations) with recent Northern Spotted Owl activity and high Barred Owl density within Northern Spotted Owl demographic study areas in Oregon and Washington, and set ARUs to record continuously each night from March to July, 2017. We reviewed spectrograms (visual representations of sound) and tagged target vocalizations to extract calls from ~160,000 hr of recordings. Even in a study area with low occupancy rates on historical territories (Washington’s Olympic Peninsula), the probability of detecting a Northern Spotted Owl when it was present in a hexagon exceeded 0.95 after 3 weeks of recording. Environmental noise, mainly from rain, wind, and streams, decreased detection probabilities for both species over all study areas. Using demographic information about known Northern Spotted Owls, we found that weekly detection probabilities of Northern Spotted Owls were higher when ARUs were closer to known nests and activity centers and when owls were paired, suggesting passive acoustic data alone could help locate Northern Spotted Owl pairs on the landscape. These results demonstrate that ARUs can effectively detect Northern Spotted Owls when they are present, even in a landscape with high Barred Owl density, thereby facilitating the use of passive, occupancy-based study designs to monitor Northern Spotted Owl populations.

中文翻译：

---

被动声学监测可在各种森林条件下有效检测北部斑点猫头鹰和条纹猫头鹰

使用自主记录单元（ARU）进行无源声学监测是野生动物研究的一个快速发展的领域，尤其是对于发声的稀有，隐秘物种。自1980年代中期以来，已经使用标记捕获方法对北部斑点猫头鹰（Strix occidentalis caurina）种群进行了监测。为了评估另一种调查方法，我们使用了ARU来检测北部斑点猫头鹰和条纹猫头鹰（S. varia）的同类动物，其范围已扩展到西北太平洋地区，并威胁到北Spot的持久性。我们将ARU设置为30 500公顷的六边形（150个ARU站），在俄勒冈州和华盛顿州的Northern Spoted Owl人口统计研究区内，Northern Spotted Owl的活动最近并且Barred Owl密度很高，并且将ARUs设置为从3月到7月的每个晚上连续记录， 2017年。我们审查了频谱图（声音的视觉表示）并标记了目标发声，以从约160,000小时的录音中提取呼叫。即使在历史领土上占用率较低的研究区域（华盛顿州的奥林匹克半岛），记录了3周后，发现六边形中有一只北极斑猫头鹰的可能性也超过了0.95。主要来自雨，风和溪流的环境噪声，在所有研究区域中两种物种的检测概率均降低。使用有关已知北斑猫头鹰的人口统计信息，我们发现，当ARU距已知巢和活动中心较近且与猫头鹰配对时，每周发现北斑猫头鹰的概率较高，这表明仅通过被动声波数据就可以帮助在其上找到北斑猫头鹰。景观。这些结果表明，即使在条纹猫头鹰密度很高的景观中，ARU仍可以有效地检测出它们的存在，从而有助于使用被动式，基于占用率的研究设计来监测北斑猫头鹰种群。我们发现，当ARU靠近已知的巢和活动中心以及猫头鹰配对时，每周发现北极斑点猫头鹰的概率较高，这表明仅被动声波数据就可以帮助在景观上定位北极斑点猫头鹰。这些结果表明，即使在条纹猫头鹰密度很高的景观中，ARU仍可以有效地检测出它们的存在，从而有助于使用被动式，基于占用率的研究设计来监测北斑猫头鹰种群。我们发现，当ARU靠近已知的巢和活动中心以及猫头鹰配对时，每周发现北极斑点猫头鹰的概率较高，这表明仅被动声波数据就可以帮助在景观上定位北极斑点猫头鹰。这些结果表明，即使在条纹猫头鹰密度很高的景观中，ARU仍可以有效地检测出它们的存在，从而有助于使用被动式，基于占用率的研究设计来监测北斑猫头鹰种群。