Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Corvallis, Oregon, USA.
Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA.
Ecol Appl. 2023 Jan;33(1):e2726. doi: 10.1002/eap.2726. Epub 2022 Nov 30.
We conducted a range-wide investigation of the dynamics of site-level reproductive rate of northern spotted owls using survey data from 11 study areas across the subspecies geographic range collected during 1993-2018. Our analytical approach accounted for imperfect detection of owl pairs and misclassification of successful reproduction (i.e., at least one young fledged) and contributed further insights into northern spotted owl population ecology and dynamics. Both nondetection and state misclassification were important, especially because factors affecting these sources of error also affected focal ecological parameters. Annual probabilities of site occupancy were greatest at sites with successful reproduction in the previous year and lowest for sites not occupied by a pair in the previous year. Site-specific occupancy transition probabilities declined over time and were negatively affected by barred owl presence. Overall, the site-specific probability of successful reproduction showed substantial year-to-year fluctuations and was similar for occupied sites that did or did not experience successful reproduction the previous year. Site-specific probabilities for successful reproduction were very small for sites that were unoccupied the previous year. Barred owl presence negatively affected the probability of successful reproduction by northern spotted owls in Washington and California, as predicted, but the effect in Oregon was mixed. The proportions of sites occupied by northern spotted owl pairs showed steep, near-monotonic declines over the study period, with all study areas showing the lowest observed levels of occupancy to date. If trends continue it is likely that northern spotted owls will become extirpated throughout large portions of their range in the coming decades.
我们使用 1993 年至 2018 年期间在 11 个研究区域收集的、涵盖亚种地理范围的调查数据，对北方斑点猫头鹰的局部繁殖率动态进行了全范围调查。我们的分析方法考虑了对猫头鹰对的不完全检测和对成功繁殖（即至少有一只幼鸟离巢）的分类错误，并进一步深入了解了北方斑点猫头鹰的种群生态学和动态。未检测到和状态分类错误都很重要，尤其是因为影响这些错误来源的因素也会影响焦点生态参数。在前一年有成功繁殖的地点，其站点占有率的年概率最大，而在前一年没有配对的地点的站点占有率最低。特定于站点的占有率转移概率随时间而下降，并且受到条纹猫头鹰存在的负面影响。总体而言，特定于站点的成功繁殖概率在年际间显示出很大的波动，并且对于在前一年经历或未经历成功繁殖的已占用站点来说是相似的。在前一年没有被占用的站点，成功繁殖的特定于站点的概率非常小。条纹猫头鹰的存在如预测的那样，对华盛顿州和加利福尼亚州的北方斑点猫头鹰的成功繁殖概率产生了负面影响，但在俄勒冈州的影响则是混合的。北方斑点猫头鹰配对占据的站点比例在研究期间急剧下降，接近单调递减，所有研究区域都显示出迄今为止观察到的最低占有率水平。如果趋势继续下去，在未来几十年中，北方斑点猫头鹰很可能会在其大部分范围内灭绝。
