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

运动可以定义为身体活动，包括持续的运动表现、心血管适应和能量消耗高于基础水平的增加。这样一个宽泛的定义在理论上可以适用于自由生活的动物的许多日常活动，例如觅食、躲避捕食者、寻找配偶、提供亲代照顾。这些活动对繁殖和生存至关重要，对自由生活的动物来说，表现不佳的代价是生死攸关的问题，不像奥运会上的人类运动员。然而，目前尚不清楚“锻炼”和“训练”等概念是否适用于自由生活的动物。自然种群中有“电视迷”和运动员吗？自由生活的动物是否通过“训练”来提高它们在健身相关活动中的表现（例如喂养小鸡）？动物如何准备和处理工作量或运动表现的快速转变（例如“从沙发上站起来”）？在一个自由生活的欧洲椋鸟（Sturnus vulgaris）种群中，我们重点研究了涉及“工作量”自然突变的两个繁殖阶段：a)成年雌鸟从孵化（相对静止）到养育雏鸟（高度活跃），b)雏鸟从雏鸟时期被迫不活动到雏鸟羽化时持续飞行。研究将整合生命史、生态学、行为学和生理学。在成虫中，我们将直接操纵工作量的成本（使用剪翅）或工作量的收益（使用取卵来延迟孵化，从而降低投资于小鸡的生殖价值）。我们将使用自动无线电跟踪全天候监测所有雌性的活动，使用加速度计，夜视和摄像机获取觅食行为的详细信息，并将其与综合生理分析（一套15个生理特征）相结合。我们将测试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的假设，即她们的“饮食”。我们还将探讨与亲代照料（例如夜间活动）相关的行为的新方面的意义。这些重要的行为是允许觅食自我维持，或者甚至是“锻炼”的机会，让鸟类为养鸡做好准备？在雏鸡中，我们将直接操纵发育（例如使用激素治疗）来验证生长速率的个体差异受生理机制约束的假设，以及羽化时的生理成熟度（而不是体细胞成熟度）是羽化后行为、飞行能力和生存的主要决定因素。此外，我们将测试小鸡使用“俯卧撑”作为羽化前锻炼的一种形式，以评估他们的体重，并确定他们所需的羽化前质量衰退，以优化羽化后的飞行能力。

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.