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).