Accounting for leg-tucking behaviour
Leg tucking was identified using raw light and immersion data streams from loggers from both single- and dual-equipped birds. Clear differences in raw immersion data can be seen from each leg of a single puffin, largely down to leg-tucking (figure 2A & 2B). Though we capture and account for much of the daylight leg-tucking using concurrent light data from the same logger (figure 2C), differences between corrected immersion time series from each leg suggests that not all leg-tucking is accounted for in this method (figure 2D & 2E). Data from both legs are therefore likely necessary to accurately identify flightless periods, i.e. primary feather moult (figure 2F). Using the dual-equipped loggers, we calculated that puffins spent 20.3% (SD = 18.9) of daylight hours tucking either or both legs, 10 times greater than the time spent in flight (1.9%, SD = 5.5). Puffins spent less than 1% of daylight hours in flight for 75% of days during the non-breeding period. Although the small sample size precluded detailed analysis, the proportion of time spent leg-tucking also varied with individual, time of year, and leg (supporting information).