Most environments undergo substantial, rhythmic changes that are at least partly predictable because of their geophysical basis. Organisms have evolved internal time-keeping mechanisms that help them anticipate, and prepare for, these rhythmic changes. Timing mechanisms are widely spread among organisms, but are implemented in species-specific ways. Migratory birds are outstanding in their ability to evade unfavourable conditions, but their mobility puts high demands on time-keeping, and on the physiological, behavioural and morphological traits that enable migration. Studies of birds in the field and captivity have revealed major contributions of inherited timing programs to seasonal processes, but no single solution that fits all species. After a general overview , I will focus on comparative work on Stonechats (Saxicola torquata), a wide-spread taxon of passerine birds that differs geographically in annual activities, including migration. I address variation in Stonechat timing programs, in the amount of seasonal plasticity, and in annual changes of behaviour and physiology, as a backdrop of the incipient genomic studies at the MPI in Ploen.