Most birds sleep while roosting at night. Although a widespread behavior, few investigators have studied the nocturnal roosting behavior of birds. Studies conducted to date have either focused on species that roost communally or used radio‐telemetry to locate sleeping individuals of a few focal species. Portable thermal cameras capable of detecting infrared (IR) heat signals may provide a more efficient and less invasive means of detecting nocturnal‐roosting endotherms such as birds. Our objective was to assess the efficacy of using thermal cameras to detect roosting birds in a woodland bird community in southeastern Australia. To better understand the limitations of using thermography to detect roosting birds, paired bird surveys were conducted along 44 transects from May to September 2016 using both traditional survey techniques during the day and surveys with a thermal camera at night. We detected 195 birds representing 21 species at nocturnal roosts using IR thermography, with the detection rate of birds during nocturnal surveys approximately one‐third (29.1%) that during diurnal surveys. Detection rates during nocturnal surveys declined more steeply with distance from observers than for diurnal surveys. Detection rates were significantly higher during diurnal surveys for 14 species of woodland birds, but did not differ between diurnal and nocturnal surveys for eight other species. Roost height, roost visibility, bird mass, and cluster size (i.e., two or more birds in physical contact) did not differ between species categorized as having high or low detectability during nocturnal surveys. Variability among species in nocturnal‐detectability could not be attributed to roost‐site visibility, roost height, or bird size. Positive detection biases associated with diurnal behavior, such as movement and vocalizations, and limitations of current IR technology, e.g., low resolution, likely contributed to overall lower detection rates during nocturnal surveys. However, our results suggest that infrared thermography can be an effective and useful technique for detecting roosting birds and studying roosting behavior, as well as for population monitoring under certain conditions.

中文翻译：

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使用红外热像仪检测夜栖鸟类

大多数鸟类在夜间栖息时会睡觉。尽管这种行为很普遍，但很少有研究者研究鸟类的夜间栖息行为。迄今为止进行的研究要么集中于共同栖息的物种，要么使用无线电遥测技术定位了几个重点物种的沉睡个体。能够检测红外（IR）热信号的便携式热像仪可能会提供一种更高效，侵入性更小的方法来检测夜间栖息的吸热物，例如鸟类。我们的目标是评估使用热像仪检测澳大利亚东南部林地鸟类群落中栖息鸟类的功效。为了更好地了解使用热像仪检测栖息鸟类的局限性，从2016年5月至2016年9月，沿44个样线进行了成对鸟类调查，白天使用传统调查技术，晚上使用热像仪进行调查。我们使用红外热成像技术在夜间栖息地中检测到195种鸟类，它们代表21种物种，夜间调查中鸟类的检出率约为昼夜调查中的三分之一（29.1％）。夜间调查中的发现率随与观察者的距离而下降的幅度比昼夜调查中的下降幅度更大。在对14种林地鸟类进行昼夜调查时，检出率显着提高，但对其他8种物种的昼夜调查和夜间调查之间的检出率没有差异。栖息地高度，栖息地可见度，鸟群质量和集群大小（即 在夜间调查中，被归类为可检测性高或低的物种之间没有差异。夜间可觉察物种之间的差异不能归因于栖息地的可见度，栖息高度或鸟类大小。与昼夜行为（例如运动和发声）相关的正检测偏差以及当前IR技术的局限性（例如，低分辨率）可能导致夜间调查期间总体检测率降低。但是，我们的结果表明，红外热成像技术可以作为一种有效且有用的技术，用于检测栖息鸟类和研究栖息行为，以及在某些条件下进行种群监测。夜间可检测物种之间的差异不能归因于栖息地的可见度，栖息高度或鸟类大小。与昼夜行为（例如运动和发声）相关的正检测偏差以及当前IR技术的局限性（例如，低分辨率）可能导致夜间调查期间总体检测率降低。但是，我们的结果表明，红外热成像技术可以作为一种有效且有用的技术，用于检测栖息鸟类和研究栖息行为，以及在某些条件下进行种群监测。夜间可检测物种之间的差异不能归因于栖息地的可见度，栖息高度或鸟类大小。与昼夜行为（例如运动和发声）相关的正检测偏差以及当前IR技术的局限性（例如，低分辨率）可能导致夜间调查期间总体检测率降低。但是，我们的结果表明，红外热成像技术可以作为一种有效且有用的技术，用于检测栖息鸟类和研究栖息行为，以及在某些条件下进行种群监测。可能导致夜间调查期间总体检出率降低。但是，我们的结果表明，红外热成像技术可以作为一种有效且有用的技术，用于检测栖息鸟类和研究栖息行为，以及在某些条件下进行种群监测。可能导致夜间调查期间总体检出率降低。但是，我们的结果表明，红外热成像技术可以作为一种有效且有用的技术，用于检测栖息鸟类和研究栖息行为，以及在某些条件下进行种群监测。