Do migratory birds need stopovers for physiological recovery?

大多数候鸟，尤其是夜间候鸟，不能在一次飞行中到达最终的迁徙目标，因此必须中途停留以积累新的燃料。中途停留通常也被认为是候鸟“休息”或从候鸟耐力飞行中恢复的时期；然而，这种休息和恢复包括什么并不为人所知。由于夜间耐力飞行，迁徙者欠下了一笔睡眠债，在破坏性的促氧化剂和保护性的抗氧化剂之间的平衡向前者转变。因此，这些生理功能需要在中途停留期间恢复似乎是合理的。我建议通过测试(I)候鸟在中途停留时是否可以改善其生理状态（氧化平衡和/或睡眠），以及（ii）离开中途停留恢复迁徙的决定是否受到鸟类生理状态的影响，从而进一步了解中途停留对候鸟的功能。在这里，我将收集草酸浓度（睡眠债务的生物标志物）和中途停留时移民的氧化平衡的纵向数据，并将这些数据与离境决定联系起来。

Most migrating birds, especially nocturnal migrants, cannot reach their final migratory goal in a single flight and thus have to make stopovers to accumulate new fuel. Stopovers are also commonly thought of as periods during which migrants 'rest' or recover from migratory endurance flight; however, what such rest and recovery encompasses is not well known. As a consequence of nocturnal endurance flight, migrants build up a sleep debt and experience a shift in the balance between damaging pro-oxidants and protective antioxidants towards the former. Therefore it seems plausible that these physiological functions need to be recovered during stopover. I propose to significantly further our understanding of the functions that stopovers have for migrating birds by testing whether (i) migrants can boost their physiological state (oxidative balance and/or sleep) while at stopover, and (ii) the decision to depart from stopover to resume migration is affected by the bird’s physiological state. Hereto, I will collect longitudinal data on oxalic acid concentrations (a bio-marker of sleep debt) and the oxidative balance of migrants at stopover as well as link these to departure decisions.