Accurate assignment of age class is critical for understanding most demographic processes. For waterfowl, most techniques for determining age class require birds in hand, reducing utility for quickly and efficiently sampling a large portion of the population. As an alternative, we sought to establish an observation‐based methodology, achievable in the field with standard optics, for determining age class of Barrow's goldeneyes (Bucephala islandica). We photographed heads, wings, and bellies of 232 Barrow's goldeneyes captured during late winter (February–April) of 2007–2015 along the north Pacific Coast. From these photographs, we focused on 5 external characteristics for both males and females, with binary states that putatively corresponded to 2 age classes—first‐year birds (<1 yr) and adults (>1 yr). For males, all 5 external traits (belly color, head color, eye color, facial crescent, median secondary coverts color) had binary states that were reliably distinguishable by observers. Moreover, all 5 external traits were highly predictive of age class (≥96% concordance between external vs. bursal‐derived ages), and novice observers, after receiving training, were able to accurately age 96% of first‐year and 99% of adult males. In contrast, patterns were weaker for females; putative external characteristics of female age class (belly color, bill radiance, bill blackness, eye color, median secondary coverts color) had 77–91% concordance with bursal‐derived age, compared with 96–100% for males, and observers misidentified age classes of 15% of females, compared with only 2% of males. Overall, age classes of male Barrow's goldeneyes were accurately and reliably distinguishable during winter based on several external characteristics, whereas those of females were not. Our technique may be used to estimate age composition of male Barrow's goldeneyes during winter, providing a useful metric for monitoring annual changes in adult‐to‐juvenile ratios and other important demographic parameters. © 2020 The Wildlife Society.

中文翻译：

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外部特征对Aarrow Barrow的Goldeneye的可靠性

准确分配年龄段对于理解大多数人口统计过程至关重要。对于水禽，大多数确定年龄等级的技术都需要鸟在手，从而降低了快速有效地对大部分人口进行采样的效用。作为替代方案，我们寻求建立一种基于观察的方法，该方法可在现场使用标准光学系统来确定巴罗金眼雀（Bucephala islandica）。我们拍摄了2007年至2015年冬末（2月至4月）在北太平洋海岸捕获的232只巴罗的金眼的头部，翅膀和腹部。从这些照片中，我们着眼于男性和女性的5个外部特征，其二元态被认为对应于2个年龄段-第一年鸟类（<1岁）和成年鸟类（> 1岁）。对于男性，所有5个外部特征（腹部颜色，头部颜色，眼睛颜色，面部新月形，中位次隐性颜色）均具有二元态，观察者可以可靠地分辨它们。此外，所有5个外部特征都可以高度预测年龄等级（外部与法人年龄之间的一致性≥96％），并且新手观察者在接受培训后能够准确地确定96％的第一年和99％的年龄。成年男性。相比之下，女性的模式则较弱。女性年龄类别的推定外部特征（腹部颜色，票据光彩，票据黑度，眼睛颜色，中等隐蔽性颜色）与法氏囊来源年龄的一致性为77–91％，而男性为96–100％，观察者误认为年龄班级中女性占15％，而男性仅为2％。总体而言，基于多种外部特征，冬季可以准确，可靠地区分雄性巴罗黄金眼的年龄类别，而雌性则不能。我们的技术可用于估计冬季巴罗雄性金眼的年龄组成，为监测成年与成年比率的年变化以及其他重要的人口统计学参数提供有用的指标。©2020野生动物协会。眼睛的颜色，中位隐秘的中位颜色）与法人派生年龄的一致性为77–91％，而男性为96–100％，观察者误认为年龄段的女性为15％，而男性仅为2％。总体而言，基于多种外部特征，冬季可以准确，可靠地区分雄性巴罗黄金眼的年龄类别，而雌性则不能。我们的技术可用于估计冬季巴罗雄性金眼的年龄组成，为监测成年与成年比率的年变化以及其他重要的人口统计学参数提供有用的指标。©2020野生动物协会。眼睛的颜色，中位隐秘的中位颜色）与法人派生年龄的一致性为77–91％，而男性为96–100％，观察者误认为年龄段的女性为15％，而男性仅为2％。总体而言，基于多种外部特征，冬季可以准确，可靠地区分雄性巴罗黄金眼的年龄类别，而雌性则不能。我们的技术可用于估计冬季巴罗雄性金眼的年龄组成，为监测成年与成年比率的年变化以及其他重要的人口统计学参数提供有用的指标。©2020野生动物协会。相比之下，男性只有2％。总体而言，基于多种外部特征，冬季可以准确，可靠地区分雄性巴罗黄金眼的年龄类别，而雌性则不能。我们的技术可用于估计冬季巴罗雄性金眼的年龄组成，为监测成年与成年比率的年变化以及其他重要的人口统计学参数提供有用的指标。©2020野生动物协会。相比之下，男性只有2％。总体而言，基于多种外部特征，冬季可以准确，可靠地区分雄性巴罗黄金眼的年龄类别，而雌性则不能。我们的技术可用于估计冬季巴罗雄性金眼的年龄组成，为监测成年与成年比率的年变化以及其他重要的人口统计学参数提供有用的指标。©2020野生动物协会。提供了一个有用的指标，用于监测成年人与青少年的比率和其他重要人口统计参数的年度变化。©2020野生动物协会。提供了一个有用的指标，用于监测成年人与青少年的比率和其他重要人口统计参数的年度变化。©2020野生动物协会。