Fueling Hummingbird Foraging: Mechanisms and Ecological Implications

为蜂鸟觅食提供燃料：机制和生态学意义加利福尼亚大学圣巴巴拉分校由于蜂鸟体型小，飞行方式耗能高，因此它们在脊椎动物中表现出一些已知的最高代谢率。低环境温度进一步增加了体温调节成本，因此增加了食物摄取率。飞到觅食地需要更高的能量消耗，那么蜂鸟是如何维持生计的呢？它们又是如何赚取能量利润来实现迁徙前的增肥呢？虽然蜂鸟依靠脂肪来为迁徙飞行提供能量，但之前对棕蜂鸟（Selasphorus rufus）的研究表明，短时间的觅食是由碳水化合物提供能量的。这使得鸟类在迁徙期间在草地上补充能量，以更高的速度储存脂肪，因为它避免了从膳食糖中合成脂肪，然后用脂肪为觅食飞行提供燃料所导致的能量效率低下。有人提出，蜂鸟最优地利用燃料，成为更高效的觅食者。在这里提出的研究中，应测量悬浮饲养期间的氧气消耗率和二氧化碳产出率，以估计悬浮饲养的能量成本，并确定所使用燃料的性质。应确定低环境温度的影响。研究结果有助于完善蜂鸟觅食能量学的计算机模型，以确定它们如何在恶劣的环境条件下获利。目前尚不清楚蜂鸟的飞行肌肉是否直接由饮食中的糖提供能量，还是饮食中的糖必须首先转化为碳水化合物的储存形式。用稳定碳同位素应使用标记的糖，以确定飞行肌肉直接由膳食糖提供燃料的程度。应检查飞行肌中糖摄取和代谢的生物化学。这项研究将涉及与国际科学家合作，在加州大学圣巴巴拉分校培训一名美国研究生，并与加州大学伯克利分校的一名西班牙裔女研究生合作。为中小学生提供生态生理学的实地研究机会。这一结果将进一步验证蜂鸟行为和新陈代谢共同适应以最大化净能量增益的假设，并将导致对蜂鸟迁徙能量学的深入了解。这些发现将有助于理解动物因全球气候变化而面临的问题。

Fueling Hummingbird Foraging: Mechanisms and Ecological ImplicationsRaul K. SuarezUniversity of California, Santa BarbaraBecause of their small size and energetically expensive mode of flight, hummingbirds display some of the highest known metabolic rates among vertebrate animals. Low ambient temperatures further increase thermoregulatory costs and, therefore, increase the rate of food intake. Flying to forage requires even higher rates of energy expenditure, so how do hummingbirds make ends meet and how do they make an energetic profit to enable pre-migratory fattening? Although hummingbirds rely on fat to fuel migratory flight, previous studies on rufous hummingbirds (Selasphorus rufus) revealed that short foraging bouts are fueled by carbohydrate. This allows birds refueling at meadows during migration to deposit fat at higher rates because it avoids the energetic inefficiency that results from synthesizing fat from dietary sugar and then using fat to fuel foraging flight. It is proposed that hummingbirds use fuels optimally to be more energetically efficient foragers. In the studies proposed here, rates of O2 consumption and CO2 production during hover-feeding shall be measured to estimate the energetic cost of hover-feeding as well as to determine the nature of the fuel(s) used. The effects of low ambient temperature shall be determined. The results shall be used to refine a computer model of the energetics of hummingbird foraging to determine how they make a profit under harsh environmental conditions. It is not known whether hummingbird flight muscles are directly fueled by dietary sugar or whether dietary sugar must first be converted into a storage form of carbohydrate. Sugar labeled with stable carbon isotope shall be used to determine the extent to which the flight muscles are fueled directly by dietary sugar. The biochemistry of sugar uptake and metabolism in flight muscles shall be examined. This research shall involve collaboration with international scientists, the training of an American graduate student at UC Santa Barbara, and collaboration with a female Hispanic graduate student at UC Berkeley. Elementary and high school students shall be provided exposure to field research in ecological physiology. The results shall allow a further test of the hypothesis that hummingbird behavior and metabolism have coadapted to maximize net energy gain and will lead to insights into the energetics of hummingbird migrations. The findings shall contribute to the understanding of the problems faced by animals as a consequence of global climate change.