Flexible flight response to challenging wind conditions in a commuting Antarctic seabird: do you catch the drift?
Résumé
Flight is intrinsically an energetically costly way of moving and birds have developed morphological,
physiological and behavioural adaptations to minimize these costs. Central-place foraging seabirds
commute regularly between nesting and foraging areas, providing us with opportunities to investigate
their behavioural response to environmental conditions that may affect flight, such as wind. Here we
tested hypotheses on how wind conditions influence flight behaviour in situations devoid of the confounding
effect that, for instance, active foraging behaviour can have on movement patterns. We studied
the Antarctic petrel, Thalassoica antarctica, a seabird breeding far inland in Antarctica and commuting
through vast ice-covered areas characterized by steady and strong winds as well as a strict absence of
foraging opportunities. We combined the three-dimensional location data from 79 GPS tracks with atmospheric
wind data over three consecutive breeding seasons (2011e2013) in order to assess individual
flight responses to wind conditions. Antarctic petrels encountered generally unfavourable winds,
particularly during return flights. Despite their capacity to adjust their speed and heading in order to
maintain constant track direction (compensation) in the strongest winds, they generally drifted as wind
strengthened. Strong winds induced low-altitude flight. Birds tended to otherwise fly relatively high, but
at altitudes with more favourable winds than what they would have encountered if flying higher. Our
results show that commuting Antarctic petrels: (1) can tolerate a certain amount of drift according to
wind conditions and (2) might be more limited by their ability to assess drift, rather than compensate for
it, at least during returning flights.