Foraging routines of small birds in winter: a theoretical investigation
Foraging routines of small birds in winter: a theoretical investigation
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小鸟冬季觅食规律：理论研究
DOI：
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发表时间：
1994
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通讯作者：
S. L. Lima
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作者：
J. McNamara;A. Houston;S. L. Lima
我们研究了饥饿和捕食这对相反的力量结合起来如何影响小型越冬鸟类的日常觅食活动。为了避免在不可预测的觅食环境中挨饿，应在一天的早些时候进行喂食，以积累最大的能量储备。然而，试图将被捕食风险降至最低的鸟类应该推迟建立能量储备，直到当天晚些时候。我们开发的动态规划模型表明，这些对立力量之间的妥协取决于食物供应中环境随机性的性质。如果（i）不可能中断觅食，并且（ii）从觅食中获得的能量相对较差，则觅食可能会在一天的早些时候达到高峰，然后稳步下降。随着能量增益的增加或觅食中断的可能性，一般的“双峰”觅食程序就会出现，在黎明和黄昏时出现活动高峰。基本的双峰惯例反映了避免捕食和饥饿之间的明显妥协，一些喂食发生在一天的早些时候和晚些时候。在许多越冬的小型鸟类中都观察到了这种双峰惯例，但对它们的解释通常不是集中在饥饿与捕食的权衡上，而是集中在食物供应或温度的日常时间模式上。我们的模型不仅表明双峰例程出现在静态环境中，而且它们对时间相关的环境变化具有鲁棒性，并且可能持续存在，例如，即使食物在中午有最大的供应。目前还没有足够的关于觅食常规的系统实证研究来对我们的预测进行彻底的检验，但现有的证据表明理论和观察之间存在普遍一致性。
We investigate the way in which the opposing forces of starvation and predation combine to influence daily foraging routines in populations of small, wintering birds. To avoid starvation in an unpredictable foraging environment, feeding should take place early in the day to accrue maximal energy reserves. However, a bird attempting to minimize its risk of predation should delay building up its energy reserves until late in the day. We develop dynamic programming models indicating that the compromise between these opposing forces depends upon the nature of environmental stochasticity in food supply. Foraging may peak early in the day and then decrease steadily if (i) interruptions in foraging are not possible, and (ii) the energetic gain from foraging is relatively poor. With a higher energetic gain, or the possibility of interruptions in foraging, a general "bimodal" foraging routine emerges, with peaks of activity around dawn and dusk. The basic bimodal routine reflects an overt compromise between the avoidance of both predation and starvation, with some feeding taking place during both the early and late portions of the day. Such bimodal routines are observed in many small, wintering birds, but explanations for them have typically focused not on starvation-predation trade-offs, but on daily temporal patterns in food availability or temperature. Our models show not only that bimodal routines emerge in static environments, but also that they are robust to time-dependent environmental variation, and may persist, for instance, even if food is maximally available during the middle of the day. There are currently not enough systematic empirical studies of foraging routines to provide a thorough test of our predictions, but available evidence suggests general agreement between theory and observation.