Temporal flexibility and consistency of daily rhythms within and between individuals in wild Great Tits <i>Parus major</i>

Organisms make use of circadian clocks to organise their daily activities. These clocks are genetically determined but are modified by environmental cues to match environmental conditions. Consistent daily rhythms (chronotypes) facilitate the anticipation for predictable situations such as the start and end of the day. In contrast, temporal flexibility allows the individual to cope with unpredictable short-term changes in the environment. Here, we aim to assess the consistency of behavioural and physiological chronotypes as well as their temporal flexibility to daylength, ambient temperature and breeding stage in a wild Great Tit population. Next, we correlated these chronotype characteristics to fitness and this way assess selection on parental daily rhythms. We monitored the daily rhythms of 26 breeding pairs on the island of Vlieland and tagged 23 males and 23 females with a temperature-sensitive radio transmitter. Additionally, data from temperature loggers to record incubation rhythms and registration of nest visits during chick provisioning were collected. From these data we extracted onset and offset as measure for daily timing of different activities (i.e. overall activity, incubation and chick provisioning, and body temperature) and linked these to fitness using data from brood monitoring. This allows us to explore selection on temporal flexibility and consistency of different chronotypes in a wild population