Diet or exercise? How do birds cope with transitions in workload associated with parental care or fledging?

运动可以被定义为身体活动，包括持续的运动能力、心血管适应能力和高于基础水平的能量消耗增加。从理论上讲，这种宽泛的定义可以适用于自由生活动物的许多日常活动，例如觅食、躲避捕食者、寻找配偶、提供父母照顾。这些活动对繁殖和生存至关重要，表现不佳的成本对自由生活的动物来说是生死攸关的问题，而不是奥运会上的人类运动员。然而，目前还不清楚“锻炼”和“训练”等概念是否适用于自由生活的动物？自然人口中有没有“电视迷”和运动员？自由生活的动物是否进行“训练”以提高它们在与健康相关的活动中的表现(例如喂小鸡)，以及动物如何准备和处理工作负荷或运动能力的快速转变(即“从沙发上站起来”)？ 在自由生活的欧洲八哥种群中，我们专注于繁殖的两个阶段，这两个阶段涉及到自然的、突然的“工作量”变化：a)成年雌性从孵化(相对久坐)到饲养小鸡(高度活跃)，以及b)从雏鸟被迫不活动到幼鸟持续飞行。研究将把生命史、生态学、行为和生理学结合起来。在成年母鸡中，我们将直接操纵工作量的成本(使用剪翼)或工作量的收益(使用去除卵子来推迟孵化，从而投资于雏鸟的繁殖价值)。我们将使用自动无线电跟踪器全天候监测所有雌性的活动，使用加速计、夜视仪和摄像机获取有关觅食行为的详细信息，并将其与全面的生理分析相结合(一套15种生理特征)。我们将检验这样的假设，即女性父母使用相对简单的生理适应(质量损失)来适应不同的工作量需求，即她们“节食”。我们还将探索与父母照顾相关的新奇行为方面的意义(例如夜间活动)。这些重要的行为是否允许觅食以自我维持，或者甚至可能是让鸟类有机会进行“锻炼”，以便为饲养雏鸟做好准备？在雏鸡身上，我们将直接控制发育(例如使用激素治疗)，以测试这样的假设，即个体生长速度的差异受到生理机制的限制，以及羽翼未成熟时的生理成熟(而不是躯体成熟)是羽毛后行为、飞行能力和生存的主要决定因素。此外，我们还将测试雏鸟将俯卧撑作为一种羽毛未丰的运动形式来评估自己的体重，并确定羽毛未丰后所需的大量后退以优化飞行能力的想法。

Exercise can be defined as physical activity involving movement supported by sustained locomotor performance, cardiovascular adaptations, and increases in energy expenditure above basal levels. Such a broad definition can theoretically be applied to many routine activities in free-living animals, e.g. foraging, escaping predators, finding mates, providing parental care. These activities are essential for reproduction and survival, and costs of under-performing' are a matter of life and death for free-living animals unlike human athletes at the Olympics. However, it's unclear if concepts such as “exercise” and “training” apply to free-living animals? Do natural populations harbour “couch potatoes” and athletes? Do free-living animals “train” to improve their performance in fitness-related activities (e.g. feeding chicks) and how do animals prepare for, and deal with, rapid transitions in workload or locomotor performance (i.e. “getting up off the couch”)? In a free-living population of European starlings (Sturnus vulgaris) we focus on two phases of breeding that involve natural, abrupt changes in “workload”: a) from incubation (relatively sedentary) to chick-rearing (highly active) in adult females, and b) from enforced inactivity as nestlings to sustained flight at fledging in young birds. Research will integrate life-history, ecology, behaviour and physiology. In adults, we will directly manipulate costs of workload (using wing-clipping) or the benefit of workload (using egg removal to delay hatching and, thus, reproductive value' of investing in chicks). We will monitor activity of all females 24/7 using an automated radio tracking, obtain detailed information on foraging behaviour using accelerometers, night-vision and video cameras, and combine this with comprehensive physiological analysis (a suite of 15 physiological traits). We will test the hypotheses that female parents use a relatively simple physiological adaptation (mass loss) to adjust to varying workload demands, i.e. they “diet”. We will also explore the significance of novel' aspects of behaviour associated with parental care (e.g. nocturnal activity). Are these important behaviours allowing foraging for self-maintenance, or perhaps even opportunities for “exercise” allowing birds to get in shape ready for chick-rearing? In chicks, we will directly manipulate development (e.g. using hormonal treatment) to test the hypothesis that individual variation in growth rate is constrained by physiological mechanisms and that physiological maturity at fledging (not somatic maturity) is the main determinant of post-fledging behaviour, flight ability and survival. In addition, we will test the idea that chicks use “push-ups” as a form of pre-fledging exercise to assess their body mass and determine their required pre-fledging mass recession to optimise flight ability after fledging.