Data from: Physiological effects of increased foraging effort in a small passerine

Foraging to obtain food, either for self-maintenance or at presumably elevated rates to provision offspring, is thought to be an energetically demanding activity but one that is essential for fitness (higher reproductive success and survival). Nevertheless, the physiological mechanisms that allow some individuals to support higher foraging performance, and the mechanisms underlying costs of high workload, remain poorly understood. We experimentally manipulated foraging behaviour in zebra finches (Taeniopygia guttata) using the technique described by Koetsier and Verhulst (2011). Birds in the “high foraging effort” (HF) group had to obtain food either while flying/hovering or by making repeated hops or jumps from the ground up to the feeder, behaviour typical of the extremely energetically-expensive foraging mode observed in many free-living small passerines. HF birds made significantly more trips to the feeder per 10min whereas control birds spent more time (perched) at the feeder. Despite this marked change in foraging behaviour we documented few short- or long-term effects of “training” (3 days and 90 days of “training” respectively) and some of these effects were sex-specific. There were no effects of treatment on BMR, hematocrit, hemoglobin, or plasma glycerol, triglyceride, glucose levels, and masses of kidney, crop, large intestine, small intestine, gizzard and liver. HF females had higher masses of flight muscle, leg muscle, heart and lung compared to controls. In contrast, HF males had lower heart mass than controls and there were no differences for other organs. When both sexes were pooled, there were no effects of treatment on body composition. Finally, birds in the HF treatment had higher levels of reactive oxygen metabolites (dROMs) and, consequently, although treatment did not affect total antioxidant capacity (OXY), birds in the HF treatment had higher oxidative stress.为获取食物而开展的觅食行为，无论是用于自身能量维持，还是以推测中更高的速率为后代储备食物，均被视为一项高能耗活动，但同时也是提升个体适合度（更高的繁殖成功率与存活率）的必要行为。然而，支撑部分个体实现更高觅食表现的生理机制，以及高工作负荷背后的成本相关机制，目前仍所知甚少。我们采用Koetsier与Verhulst（2011）所描述的实验方法，对斑胸草雀（Taeniopygia guttata）的觅食行为进行了实验操控。“高觅食努力（HF）”组的个体必须通过飞行/悬停，或是反复从地面跳跃至取食器的方式获取食物——这一行为模式与许多自由生活的小型雀形目鸟类所采用的极耗能觅食方式高度相似。HF组鸟类每10分钟前往取食器的频次显著更高，而对照组鸟类则在取食器处停留（栖息）的时间更长。尽管觅食行为发生了显著改变，但我们仅记录到少量由“训练”（分别为3天与90天的训练时长）带来的短期与长期效应，且部分效应存在性别特异性。实验处理对基础代谢率（BMR）、红细胞比容、血红蛋白，以及血浆甘油、甘油三酯、葡萄糖水平，与肾脏、嗉囊、大肠、小肠、肌胃和肝脏的重量均无显著影响。与对照组相比，HF组雌性个体的飞行肌、腿部肌肉、心脏及肺脏重量均显著更高。与之相反，HF组雄性个体的心脏重量低于对照组，其余器官重量则无组间差异。若将两性个体合并分析，实验处理对身体组成无显著影响。最后，HF组鸟类的活性氧代谢物（dROMs）水平更高；因此，尽管实验处理对总抗氧化能力（OXY）无影响，但HF组鸟类的氧化应激水平更高。