MONITORING RESULTS OF NORTHERN GOSHAWK NESTING AREAS IN THE GREATER YELLOWSTONE ECOSYSTEM: IS DECLINE IN OCCUPANCY RELATED TO HABITAT CHANGE
MONITORING RESULTS OF NORTHERN GOSHAWK NESTING AREAS IN THE GREATER YELLOWSTONE ECOSYSTEM: IS DECLINE IN OCCUPANCY RELATED TO HABITAT CHANGE
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大黄石生态系统中北方灰鹰筑巢区的监测结果：占用率下降是否与栖息地变化有关
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发表时间：
2008
期刊：
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通讯作者：
Patla
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作者：
M. Susan;Patla
-从19982002(最近)起，我监测了爱达荷州东部和怀俄明州西部Cariou-Targhee国家森林的Targhee部分的北沙鹰(Accipiter Gentilis)筑巢区域的子集，以提供入住率和生产力数据，以满足美国林务局的监测要求。每年对随机选择的16个筑巢区进行调查，其中一半在未受干扰的地区，另一半在木材销售项目区。1998-2002年的平均入住率为34%，大大低于1992-95年(基准期)在这些筑巢地区使用类似调查方法和努力测得的61%。在这两个时期，成功筑巢的生产力相似。除了标准的广播调查方法外，我还在2001-02年使用了黎明发声调查方法，以确定入住率低是否反映了占用场地但未能复制的配对的检测率较低。在这两年的求偶期间，苍鹰的平均发现率不到50%，这表明调查到的重新占据已知筑巢区域的苍鹰数量很少。我发现天气因素和较低的入住率之间没有关系。位于过去木材采伐区的筑巢区域的占有率在最近一段时间显著低于较少干扰生境的筑巢区的占有率(分别为22%和45%)，这表明占有率可能受到木材管理做法的长期影响。近期观察到的下降是否反映了筑巢对的空间变化、对天气或猎物变化的短期人口统计反应、或对木材管理活动引起的森林结构和年龄变化的较长期反应，无法使用目前的监测方案确定。根据统计上有效的研究设计和足够的样本量，需要对美国西部研究地区进行长期监测，以了解这里和最近其他研究报告中苍鹰占有率的明显下降是否对该物种的保护产生了严重影响。
--I monitored a subset of Northern Goshawk (Accipiter gentilis) nesting areas on the Targhee portion of the Caribou-Targhee National Forest in eastern Idaho and western Wyoming from 19982002 (recent period) to provide occupancy and productivity data for U.S. Forest Service monitoring requirements. A total of 16 randomly-selected nesting areas, half in undisturbed and half in timber-sale project areas, were surveyed each year. Occupancy in 1998-2002 averaged 34%, which was significantly lower than the 61% measured at these nesting areas from 1992-95 (baseline period) using similar survey methods and effort. Productivity of successful nests was similar between the two periods. I used the dawn vocalization survey method in 2001-02, in addition to standard broadcast survey methods, to determine if low occupancy reflected a poor detection rate of pairs that occupied sites, but failed to reproduce. Detection rate of goshawks during the courtship period in these 2 yr averaged less than 50%, indicating that number of pairs reoccupying known nesting areas surveyed was low. I found no relation between weather factors and lower occupancy. Occupancy at nesting areas located in past timber-harvest areas in the recent period was significantly lower compared to those in less disturbed habitat (22% occupancy versus 45%, respectively) suggesting that occupancy may be influenced by the longterm effects of timber-management practices. Whether the observed decline during the recent period reflects spatial shifts of nesting pairs, short-term demographic responses to variation in weather or prey, or longer-term responses to changes in forest structure and age resulting from timber-management activities, cannot be determined using the current monitoring program. Long-term monitoring of study areas in the western United States, based on statistically valid study designs and adequate sample size, is needed to understand if the apparent decline in goshawk occupancy reported here and in other recent studies has serious implications for conservation of this species.