The whooping crane (Grus americana), an endangered species, has been counted on its winter grounds in Texas, USA, since 1950 using fixed‐wing aircraft. Many shortcomings of the traditional survey technique have been identified, calling into question its efficacy, defensibility, repeatability, and usefulness into the future. To improve and standardize monitoring effort, we began investigating new survey techniques. Here we focus on efficacy of line transect‐based distance sampling during aerial surveys. We conducted a preliminary test of distance sampling during winter 2010–2011 while flying the traditional survey, which indicated that detectability within 500 m of transects was 0.558 (SE = 0.031). We then used an experimental decoy survey to evaluate impacts of observer experience, sun position, distance from transect, and group size on detectability. Our results indicated decoy detectability increased with group size and exhibited a quadratic relationship with distance likely due to pontoons on the aircraft. We found that detectability was 2.704 times greater when the sun was overhead and 3.912 times greater when the sun was at the observer's back than when it was in the observer's eyes. We found that an inexperienced observer misclassified non‐target objects more often than an experienced observer. During the decoy experiment we used marks on the struts to categorize distances into intervals, but we found that observers misclassified distances 46.7% of the time (95% CI = 37.0–56.6%). Also, we found that detectability of individuals within detected groups was affected by group size and distance from transect. We discuss how these results inform design and implementation of future whooping crane monitoring efforts. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

中文翻译：

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使用航空勘测监测鸣鹤数量：对可检测性的影响。


美洲鹤 ( Grus americana ) 是一种濒临灭绝的物种，自 1950 年以来一直使用固定翼飞机在美国德克萨斯州的冬季场地进行清点。传统调查技术的许多缺点已经被发现，使其有效性、防御性、可重复性和未来的有用性受到质疑。为了改进和标准化监测工作，我们开始研究新的调查技术。在这里，我们重点关注航空测量期间基于线样线的距离采样的有效性。我们在2010-2011年冬季进行了传统调查时距离采样的初步测试，结果表明样线500 m内的可探测性为0.558（SE = 0.031）。然后，我们使用实验性诱饵调查来评估观察者经验、太阳位置、距样线的距离以及群体规模对可探测性的影响。我们的结果表明，诱饵的可探测性随着群体规模的增加而增加，并且与距离呈二次关系，这可能是由于飞机上的浮桥所致。我们发现，当太阳在头顶时，可探测性比在观察者眼睛中时高 2.704 倍，当太阳在观察者背后时，可探测性高 3.912 倍。我们发现，缺乏经验的观察者比经验丰富的观察者更容易对非目标对象进行错误分类。在诱饵实验中，我们使用支柱上的标记将距离分类为间隔，但我们发现观察者有 46.7% 的时间对距离进行了错误分类（95% CI = 37.0–56.6%）。此外，我们发现检测组内个体的可检测性受到组大小和距样线距离的影响。我们讨论这些结果如何为未来美洲鹤监测工作的设计和实施提供信息。 2013 年发表。本文为美国 在美国，政府工作属于公共领域。