Density-Dependence in the Survival and Reproduction of Bald Eagles: Linkages to Chum Salmon
Density-Dependence in the Survival and Reproduction of Bald Eagles: Linkages to Chum Salmon
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DOI：
10.1002/jwmg.233
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发表时间：
2011-11-01
影响因子：
2.3
通讯作者：
Stenerson, Ken
中科院分区：
文献类型：
--
作者：
Elliott, Kyle Hamish;Elliott, John E.;Stenerson, Ken
在20世纪后期，由于污染和迫害的减少，秃鹰（halaeetus leucocephalus）的数量急剧增加。目前，调控鹰群的机制尚不清楚。为了研究太平洋西北地区潜在的调节过程，在那里鹰不再主要受到污染物或直接迫害的控制，我们研究了秃鹰的繁殖成功率、繁殖种群、冬季种群、死亡率和鲑鱼流的使用。20世纪80年代初至90年代末，不列颠哥伦比亚省南部沿海的越冬和繁殖鹰的数量翻了两番，此后一直稳定下来。在1986-2009年期间，密度依赖性的繁殖下降发生，但不是通过立地质量的变化。冬季中期的生存是至关重要的，因为大多数死亡发生在那时，模型显示，人口增长率的密度依赖性下降部分是由于存活率的降低。不列颠哥伦比亚省的越冬鹰以鲑鱼（Oncorhynchus keta）为食，然后在死亡率最高的冬末转向鸟类。当鲑鱼从阿拉斯加迁徙到北华盛顿时，鹰往往会在BC省溪流中鲑鱼数量达到高峰后到达。在阿拉斯加寒冷的冬季和鲑鱼大量供应的年份，鹰在不列颠哥伦比亚省南部最为丰富。我们认为，太平洋西北地区的鹰数量目前部分受到繁殖地密度的限制，部分受到冬末成年鹰死亡率的限制，可能是由于冬末鲑鱼种群减少，迫使鹰利用更多边缘猎物供应。大鹰的数量已经影响了一些当地猎物的数量。(C) 2011野生动物协会。
During the late 20th Century, due to decreases in both contamination and persecution, bald eagle (Haliaeetus leucocephalus) populations increased dramatically. Currently, mechanisms regulating eagle populations are not well understood. To examine potential regulating processes in the Pacific Northwest, where eagles are no longer primarily regulated by contaminants or direct persecution, we examined bald eagle reproductive success, breeding populations, winter populations, mortality, and salmon stream use. Wintering and breeding eagle populations in south-coastal British Columbia (BC) quadrupled between the early 1980s and the late 1990s, and have since stabilized. Density-dependent declines in reproduction occurred during 1986-2009, but not through changes in site quality. Mid-winter survival was crucial as most mortality occurred then, and models showed that density-dependent reductions in population growth rates were partially due to reduced survival. Wintering eagles in British Columbia fed heavily on chum salmon (Oncorhynchus keta) runs, and then switched to birds in late winter, when mortality was highest. Eagles tended to arrive after the peak in salmon availability at streams in BC as part of a migration associated with salmon streams from Alaska to northern Washington. Eagles were most abundant in southern BC during cold Alaskan winters and in years of high chum salmon availability. We suggest that eagle populations in the Pacific Northwest are currently partially limited by density on the breeding grounds and partially by adult mortality in late winter, likely due to reduced late winter salmon stocks forcing eagles to exploit more marginal prey supplies. Larger eagle populations have affected some local prey populations. (C) 2011 The Wildlife Society.