Boreal bird abundance estimates within different energy sector disturbances vary with point count radius

Responses of boreal birds to changes in forest structure and composition caused by construction of well pads, seismic lines, and pipelines are poorly understood. Bird species associated with older forests are predicted to experience larger population declines with increased disturbance compared with species associated with younger or open habitats; however, point count methods may influence apparent outcomes because the proportional area of disturbed vegetation and the magnitude, uncertainty, and detection of a disturbance response by birds vary as a function of sampling area. We analyzed point count data from 12 energy sector studies and measured how disturbance type and point count radius interacted to affect 531 impact ratios (mean abundance at point counts centered within disturbances relative to abundance at point counts within forest 150-400 m from the nearest edge bordering those disturbances [59 species*3 disturbance types*3 point count radii]). We observed larger disturbance effects (impact ratios) within larger-radius point counts at well pads (100-m and unlimited-distance) and pipelines (unlimited-distance) compared with 50-m point counts at seismic lines, and within 50-m point counts at well pads relative to 50-m point counts at seismic lines. Effect uncertainty was higher at well pads and pipelines than seismic lines, and lower within larger-radius point counts. The probability of detecting a disturbance response was greater for larger-radius point counts at pipelines than for 50-m point counts at seismic lines, and within 50-m point counts at well pads relative to 50-m point counts at seismic lines. On average, a species was more likely to increase in abundance near an energy sector disturbance if the species was not associated with older (>75 yr) forest stages. While the effects of disturbance varied by species and with disturbance type, the effects of pipelines and seismic lines were better detected by larger-radius point counts, while the effects of well pads were better detected by smaller-radius point counts.

北方鸟类对因井场、地震测线和管道建设而导致的森林结构和组成变化的反应，人们知之甚少。与老龄森林相关的鸟类物种预计随着干扰增加，其种群数量下降幅度会比与较年轻或开阔栖息地相关的物种更大；然而，样点计数法可能会影响表观结果，因为受干扰植被的面积比例以及鸟类对干扰反应的程度、不确定性和可检测性会随着采样面积的变化而变化。我们分析了来自12项能源部门研究的样点计数数据，并测量了干扰类型和样点计数半径如何相互作用以影响531个影响比率（以干扰区域为中心的样点计数处的平均丰度相对于距离与这些干扰相邻的最近边缘150 - 400米的森林内样点计数处的丰度[59个物种×3种干扰类型×3个样点计数半径]）。我们观察到，在井场（100米和无限制距离）和管道（无限制距离）的较大半径样点计数中，与地震测线的50米样点计数相比，以及在井场的50米样点计数相对于地震测线的50米样点计数，干扰效应（影响比率）更大。井场和管道的效应不确定性高于地震测线，且在较大半径样点计数中较低。在管道的较大半径样点计数中检测到干扰反应的概率比在地震测线的50米样点计数中更大，并且在井场的50米样点计数相对于地震测线的50米样点计数也是如此。平均而言，如果一个物种与老龄（>75年）森林阶段无关，那么它在能源部门干扰附近数量更有可能增加。虽然干扰的影响因物种和干扰类型而异，但管道和地震测线的影响通过较大半径样点计数能更好地检测到，而井场的影响通过较小半径样点计数能更好地检测到。