Food-limitation in a generalist predator
Food-limitation in a generalist predator
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通才捕食者的食物限制
DOI：
10.1098/rspb.2006.3507
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
R. Bijlsma
中科院分区：
文献类型：
--
作者：
C. Rutz;R. Bijlsma
调查食物限制在通才捕食者是困难的，因为他们可以切换到替代猎物，当他们的主食之一变得稀缺。除了捕食者种群的动态数据，一个强大的研究需要：（一）捕食者的整个猎物基地的文件;（二）实验或自然的情况下，有利可图的饮食变化是不可能的，因为几个首选的猎物物种同时下降。在这里，我们提供了一个详细的描述，如何食物供应有限的多面手鸟类顶级捕食者，北方苍鹰。在我们的研究区域，几个主要的苍鹰猎物物种的人口同时崩溃在1975-2000年，而其他外在因素基本保持不变。当地苍鹰种群的繁殖和非繁殖部分明显下降，与显着增加的巢失败。成功对的育雏大小保持不变的变化，猎物的可用性。繁殖招募停止时，潜在的替代鸟类（“飞蚊症”）仍然存在，提供了一个罕见的经验证明的“接受阈值”猛禽领土的选择。为了研究苍鹰的饮食是如何随着食物供应的变化而变化的，我们使用了生物多样性研究中的一种新的分析工具--“丰度-生物量-比较曲线”（ABC曲线）。随着食物压力水平的增加，主要猎物物种在饮食中的优势度下降，小型猎物物种的数量增加，行会内捕食。我们的发现，育种和非育种部分下降的音乐会是出乎意料的。我们的研究结果进行管理的含义，在食物有限的猛禽种群，外部诱导的繁殖者死亡率可以迅速降低人口规模，损失不再缓冲时，飞蚊拒绝繁殖的机会。
Investigating food-limitation in generalist predators is difficult, because they can switch to alternative prey, when one of their staple prey becomes scarce. Apart from data on the dynamics of the predator population, a robust study requires: (i) a documentation of the predator's entire prey base; and (ii) an experimental or natural situation, where profitable dietary shifts are impossible, because several preferred prey species decline simultaneously. Here, we provide a detailed description of how food-supply has limited a generalist avian top predator, the northern goshawk Accipiter gentilis. In our study area, populations of several principal goshawk prey species crashed simultaneously during 1975–2000, whereas other extrinsic factors remained essentially unchanged. The breeding and non-breeding segments of the local goshawk population declined markedly, associated with a significant increase in nest failures. Brood size of successful pairs remained unaffected by changes in prey availability. Breeding recruitment ceased at a time when potential replacement birds (‘floaters’) were still present, providing a rare empirical demonstration of an ‘acceptance threshold’ in raptor territory choice. To investigate how goshawk diet changed in response to varying food-supplies, we make novel use of an analytical tool from biodiversity research—‘abundance–biomass–comparison curves’ (ABC curves). With increasing levels of food-stress, the dominance of principal prey species in the diet decreased, and the number of small-bodied prey species increased, as did intra-guild predation. Our finding that breeder and non-breeder segments declined in concert is unexpected. Our results carry the management implication that, in food-limited raptor populations, externally induced breeder mortality can rapidly depress population size, as losses are no longer buffered when floaters reject breeding opportunities.