Baasch David M, Hefley Trevor J, Cahis Staci D
Headwaters Corporation 4111 4th Avenue Suite 6 Kearney Nebraska 68845.
Ecol Evol. 2015 Sep 4;5(18):4197-209. doi: 10.1002/ece3.1680. eCollection 2015 Sep.
For many species, breeding population size is an important metric for assessing population status. A variety of simple methods are often used to estimate this metric for ground-nesting birds that nest in open habitats (e.g., beaches, riverine sandbars). The error and bias associated with estimates derived using these methods vary in relation to differing monitoring intensities and detection rates. However, these errors and biases are often difficult to obtain, poorly understood, and largely unreported. A method was developed to estimate the number of breeding pairs using counts of nests and broods from monitoring data where multiple surveys were made throughout a single breeding season (breeding pair estimator; BPE). The BPE method was compared to two commonly used estimation methods using simulated data from an individual-based model that allowed for the comparison of biases and accuracy. The BPE method underestimated the number of breeding pairs, but generally performed better than the other two commonly used methods when detection rates were low and monitoring frequency was high. As detection rates and time between surveys increased, the maximum nest and brood count method performs similar to the BPE. The BPE was compared to four commonly used methods to estimate breeding pairs for empirically derived data sets on the Platte River. Based on our simulated data, we expect our BPE to be closest to the true number of breeding pairs as compared to other methods. The methods tested resulted in substantially different estimates of the numbers of breeding pairs; however, coefficients from trend analyses were not statistically different. When data from multiple nest and brood surveys are available, the BPE appears to result in reasonably precise estimates of numbers of breeding pairs. Regardless of the estimation method, investigators are encouraged to acknowledge whether the method employed is likely to over- or underestimate breeding pairs. This study provides a means to recognize the potential biases in breeding pair estimates.
对于许多物种而言，繁殖种群规模是评估种群状况的一项重要指标。对于在开阔栖息地（如海滩、河漫滩）筑巢的地面筑巢鸟类，通常会使用多种简单方法来估算这一指标。使用这些方法得出的估计值所关联的误差和偏差，会因监测强度和检测率的不同而有所变化。然而，这些误差和偏差往往难以获取、了解甚少且大多未被报告。开发了一种方法，利用在单个繁殖季节进行多次调查所获监测数据中的巢穴和窝雏数量来估算繁殖对数量（繁殖对估计器；BPE）。使用基于个体模型的模拟数据将BPE方法与两种常用估计方法进行了比较，该模型允许对偏差和准确性进行比较。BPE方法低估了繁殖对数量，但在检测率较低且监测频率较高时，总体表现优于其他两种常用方法。随着检测率和调查间隔时间的增加，最大巢穴和窝雏数量法的表现与BPE相似。将BPE与四种常用方法进行比较，以估算普拉特河经验性数据集的繁殖对数量。基于我们的模拟数据，我们预计与其他方法相比，我们的BPE最接近繁殖对的真实数量。所测试的方法得出的繁殖对数量估计值差异很大；然而，趋势分析的系数在统计上并无差异。当有多组巢穴和窝雏调查数据可用时，BPE似乎能得出相当精确的繁殖对数量估计值。无论采用何种估计方法，都鼓励研究人员说明所采用的方法可能会高估还是低估繁殖对数量。本研究提供了一种认识繁殖对估计中潜在偏差的方法。
