Testing single leg data in dual-equipped birds
A similar moult identification method was attempted using data from each
dual-equipped logger in isolation. As before, the proportion of time
spent wet was corrected for tucking behaviour using raw light signals.
Any points with a solar angle below -3 degrees were omitted for this
analysis, to ensure that leg-tucking was sufficiently captured using
light data. Propflight and propflight-5were again calculated, and the same incrementing threshold method was
used to identify putative moult periods of minimum 30 days duration. A
maximum threshold value of 1% propflight-5 was applied
to restrict the likelihood of
falsely identifying moult from noisy immersion time series. This meant
that the 5-day rolling average of corrected flight, or
propflight-5, had to remain below 1% for a period to be
considered as moult. Independently derived inferred moult periods were
compared to combined data from dual-equipped loggers. Based on limited
but good agreement (see results), the process was then applied to the
geolocator data collected from 40 individuals equipped with single
loggers from Skellig Michael, Ireland.
Observations from captive
puffins
Several aquaria house captive puffins as part of displays. Aquarists
from 3 of these facilities provided observations about moulting habits
of their captive puffins to contextualise our results and test whether
our conclusions were physiologically viable. We spoke to aquarists from
Tierpark Bern, Switzerland, the National Aquarium, USA, and Oceanário de
Lisboa, Portugal. All described variation in moulting behaviour, see
details in supporting information. Further relevant observations are
referenced as personal communications in the main text.