Demographic response of northern spotted owls to barred owl removal
Demographic response of northern spotted owls to barred owl removal
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DOI：
10.1002/jwmg.1046
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发表时间：
2016-05-01
影响因子：
2.3
通讯作者：
McDonald, Trent L.
中科院分区：
文献类型：
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作者：
Diller, Lowell V.;Hamm, Keith A.;McDonald, Trent L.
1990年被联邦政府列为濒危物种，主要是因为栖息地的丧失，北方斑点猫头鹰（Strix oceanentalis caurina）继续下降，尽管保护工作导致森林栖息地被保留在整个范围内。最近，有越来越多的证据表明，同源入侵横斑猫头鹰（Strix varia）可能是持续下降的主要原因，因为它将斑点猫头鹰排除在其首选栖息地之外。我们使用了一个长期的人口统计学研究，发现在沿海北方加州的基础上，试点禁止猫头鹰删除实验。我们的人口统计学研究使用了从1990年到2013年收集的捕获-再捕获，生殖输出和领土占用数据，以评估人口动态率和人口的趋势。我们使用了一个经典的前后控制影响（BACI）的实验设计，调查人口的北方斑点猫头鹰的致命去除横斑猫头鹰的反应。根据最佳2种动态占用模型，没有证据表明在治疗开始前（去除条纹猫头鹰），条纹猫头鹰或北方斑点猫头鹰占用率存在差异。处理后，禁止猫头鹰占用率较低，在处理相对于未处理的地区和斑点猫头鹰占用率较高，相对于未处理的地区。禁止猫头鹰拆除减少斑点猫头鹰领土灭绝率，但不影响领土殖民率。因此，斑点猫头鹰的占有率在处理过的地区增加，在未处理过的地区继续下降。之前和之后禁止猫头鹰删除，没有证据表明，平均繁殖力不同的2个研究领域。然而，更多的被占领的斑点猫头鹰网站上的治疗领域导致更大的生产力在治疗领域的基础上经验计数的羽翼丰满的年轻。在移除之前，处理和未处理区域的存活率以每年约0.2%的速度下降。处理后，处理区域的估计存活率为0.859，未处理区域为0.822。对两个研究地区的人口变化得出的估计数显示，在搬迁前，人口普遍下降，估计斜率为每年-0.0036。清除后，处理区的种群变化率增加到平均1.029，但未处理区的平均下降到0.870。第一次实验的结果表明，在我们研究区域的处理部分，对横斑猫头鹰进行致死性清除可以恢复北方斑点猫头鹰种群。如果其他联邦资助的禁止猫头鹰去除实验提供了类似的结果，这可能是一个长期的保护策略，北方斑点猫头鹰发展的基础。(c)2016野生动物协会
Federally listed as threatened in 1990 primarily because of habitat loss, the northern spotted owl (Strix occidentalis caurina) has continued to decline despite conservation efforts resulting in forested habitat being reserved throughout its range. Recently, there is growing evidence the congeneric invasive barred owl (Strix varia) may be responsible for the continued decline primarily by excluding spotted owls from their preferred habitat. We used a long-term demographic study for spotted owls in coastal northern California as the basis for a pilot barred owl removal experiment. Our demography study used capture-recapture, reproductive output, and territory occupancy data collected from 1990 to 2013 to evaluate trends in vital rates and populations. We used a classic before-after-control-impact (BACI) experimental design to investigate the demographic response of northern spotted owls to the lethal removal of barred owls. According to the best 2-species dynamic occupancy model, there was no evidence of differences in barred or northern spotted owl occupancy prior to the initiation of the treatment (barred owl removal). After treatment, barred owl occupancy was lower in the treated relative to the untreated areas and spotted owl occupancy was higher relative to the untreated areas. Barred owl removal decreased spotted owl territory extinction rates but did not affect territory colonization rates. As a result, spotted owl occupancy increased in the treated area and continued to decline in the untreated areas. Prior to and after barred owl removal, there was no evidence that average fecundity differed on the 2 study areas. However, the greater number of occupied spotted owl sites on the treated areas resulted in greater productivity in the treated areas based on empirical counts of fledged young. Prior to removal, survival was declining at a rate of approximately 0.2% per year for treated and untreated areas. Following treatment, estimated survival was 0.859 for the treated areas and 0.822 for the untreated areas. Derived estimates of population change on both study areas showed the same general decline before removal with an estimated slope of -0.0036 per year. Following removal, the rate of population change on the treated areas increased to an average of 1.029 but decreased to an average of 0.870 on the untreated areas. The results from this first experiment demonstrated that lethal removal of barred owls allowed the recovery of northern spotted owl populations in the treated portions of our study area. If additional federally funded barred owl removal experiments provide similar results, this could be the foundation for development of a long-term conservation strategy for northern spotted owls. (c) 2016 The Wildlife Society.