Aerial surveys for waterfowl and other waterbirds provide abundance estimates that are commonly used by state and federal agencies for waterfowl and wetland management. However, most existing surveys provide an index of abundance and are uncorrected for visibility bias, which may limit their use in accurately determining local population size. We used concurrent ground and aerial surveys to estimate visibility bias during cruise‐style waterfowl surveys from September through January 2014–2017 along the Illinois River Valley, Illinois, USA. Immediately before an aerial survey, a ground observer counted waterfowl and other waterbirds by species within a distinct survey area and counts were compared with aerial abundance estimates to quantify detection rate and count bias (i.e., visibility bias). Overall, waterfowl guilds had high detection rates and low count bias, resulting in low overall visibility bias (ducks, −11% [SE = 5%]; geese, −8% [SE = 3%]; swans, −5% [SE = 3%]). At the species level, visibility bias varied greatly (e.g., green‐winged teal [Anas crecca], 182% [SE = 221%]; American wigeon [Mareca americana], −74% [SE = 20%]). Group size, species prevalence, cloud cover, and temperature influenced visibility bias, but direction and magnitude of effects were variable among taxa. Low visibility bias for most guilds indicated that well‐designed, cruise‐style aerial surveys with bias estimation techniques provided reliable estimates of population size and have great utility for monitoring waterfowl and other waterbirds as part of an adaptive management framework. © 2021 The Wildlife Society.

中文翻译：

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非繁殖季节水鸟在空中勘测中的能见度偏差

对水禽和其他水鸟的航测提供了丰度估计，州和联邦机构通常将其用于水禽和湿地管理。但是，大多数现有调查提供了一个丰度指标，并且没有针对可见度偏差进行校正，这可能会限制它们在准确确定本地人口规模方面的使用。我们在2014年9月至2014年1月至2014年1月至2017年1月的美国伊利诺伊州伊利诺伊河谷进行的巡航式水禽调查中，使用了同时进行的地面和空中调查来估计能见度偏差。在进行航空测量之前，地面观察员立即在不同的测量区域内按物种对水禽和其他水鸟进行了计数，并将计数与航空丰度估计值进行了比较，以量化检测率和计数偏差（即可见度偏差）。全面的，水禽行会的检出率高，计数偏倚低，导致总体可见度偏低（鸭子，-11％[SE = 5％]；鹅，-8％[SE = 3％]；天鹅，-5％[SE = 3％]）。在物种级别，可见度偏差变化很大（例如，绿翅蓝绿色[Anas crecca ]，182％[SE = 221％]；美国假发[ -Mareca americana ]，-74％[SE = 20％]）。种群大小，物种流行度，云量和温度影响可见度偏差，但影响的方向和幅度在分类单元中是可变的。对于大多数行会来说，可见性偏低的现象表明，经过精心设计的，带有偏差估计技术的巡游式航测提供了可靠的种群数量估计，并且作为自适应管理框架的一部分，对于监视水禽和其他水鸟具有巨大的实用性。©2021野生动物协会。