Cornell Laboratory of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA.
Proc Biol Sci. 2013 Apr 17;280(1760):20123087. doi: 10.1098/rspb.2012.3087. Print 2013 Jun 7.
Daily patterns in the foraging behaviour of birds are assumed to balance the counteracting risks of predation and starvation. Predation risks are a function of the influence of weight on flight performance and foraging behaviours that may expose individuals to predators. Although recent research sheds light on daily patterns in weight gain, little data exist on daily foraging routines in free-living birds. In order to test the predictions of various hypotheses about daily patterns of foraging, we quantified the activity of four species of passerines in winter using radio-frequency identification receivers built into supplemental feeding stations. From records of 472,368 feeder visits by tagged birds, we found that birds generally started to feed before sunrise and continued to forage at a steady to increasing rate throughout the day. Foraging in most species terminated well before sunset, suggesting their required level of energy reserves was being reached before the end of the day. These results support the risk-spreading theorem over a long-standing hypothesis predicting bimodality in foraging behaviour purportedly driven by a trade-off between the risks of starvation and predation. Given the increased energetic demands experienced by birds during colder weather, our results suggest that birds' perceptions of risk are biased towards starvation avoidance in winter.
鸟类的觅食行为模式通常被认为是在捕食和饥饿风险之间取得平衡的结果。捕食风险是体重对飞行性能和觅食行为影响的函数，这些行为可能会使个体暴露于捕食者面前。尽管最近的研究揭示了体重增加的日变化模式，但关于自由生活鸟类的日常觅食习惯的数据很少。为了检验关于觅食日变化模式的各种假设的预测，我们使用内置在补充喂养站中的射频识别接收器来量化冬季四种雀形目鸟类的活动。从标记鸟类 472,368 次喂食访问的记录中，我们发现鸟类通常在日出前开始觅食，并在白天持续以稳定或增加的速度觅食。大多数物种的觅食活动在日落前就结束了，这表明它们在一天结束前达到了所需的能量储备水平。这些结果支持了风险分散理论，该理论长期以来一直预测觅食行为的双峰模式，据称这是由饥饿和捕食风险之间的权衡驱动的。考虑到鸟类在寒冷天气下经历的能量需求增加，我们的结果表明，鸟类在冬季对风险的感知偏向于避免饥饿。
