Measurements of immune function in migrating birds from Recovery of constitutive immune function after migratory endurance flight in free-living birds

Strenuous physical activity can negatively affect constitutive innate immune function (CIF), the always present first line of defence against pathogens. CIF is non-specific, and thus vital when encountering novel pathogens. A lowered CIF likely increases the risk of infection and disease. Migratory birds engage in truly extreme physical activity during their endurance flights, however, little is known about how they deal with the negative impact this has on their immune function. By collecting both between- and within-individual data we show, for the first time, that free-flying migratory birds can recover several parameters of CIF during stopovers, which are stationary periods in between migratory flights. With this, we provide an important piece of the puzzle on how migrating birds cope with the physiological challenges they face on their biannual journeys. Furthermore, our study stresses the importance of migratory stopovers beyond fuel accumulation.高强度体力活动会对组成型固有免疫功能（constitutive innate immune function，CIF）产生负面影响，该功能是机体始终存在的抵御病原体的第一道防线。CIF不具备特异性，因此在遭遇新型病原体时至关重要。CIF水平下调可能会提升感染与患病风险。候鸟在长距离耐力飞行过程中会开展极端高强度的体力活动，但目前学界对它们如何应对此类活动对免疫功能造成的负面影响仍知之甚少。本研究通过收集个体间与个体内的双重数据，首次证实自由飞行的候鸟能够在迁徙中途停留期间恢复多项CIF相关参数——此类停留是两次迁徙飞行之间的静止休整阶段。借此，我们为解开候鸟如何应对其每年两次迁徙途中面临的生理挑战这一科学谜题提供了关键一环。此外，本研究还强调，迁徙中途停留的重要性远超单纯的能量积累过程。