Fine-scale flight: the effect of wind on flight patterns of dynamic soaring seabirds

Abstract

**Abstract:** Technological advances in biologging in recent years have opened several new avenues to study the at-sea behaviour of seabirds. The efficiency and size of these loggers have been improved to such an extent that fine-scale behavioural data can be recorded for extended periods. This is particularly useful when studying the at-sea behaviour of far-ranging Procellariiformes, a task that is often logistically challenging. We used a combination of biologgers (GPS, video camera and inertial measurement units [IMUs]) to study the flight behaviour of several procellariiforms breeding on sub-Antarctic Islands in the southern Indian and Atlantic Oceans, in varying wind conditions. The IMUs (including tri-axial accelerometers and magnetometers) allowed us to infer fine-scale (40 Hz) movement patterns while the video cameras were used to ground-truth the IMUs and to extract bank angles from recorded flights. Dynamic soaring was identified through sinusoidal curves in magnetometer axes (independent of acceleration), while individual flaps were identified from the heave axis of the accelerometer. GPS loggers provided hourly location estimates, which were used to determine local wind conditions from satellite data. Albatrosses displayed dynamic soaring during most flights, with the duration of cycles decreasing and bank angles increasing with increasing wind speeds. By coupling flapping and roll angles we show that flapping, on occasion, occur at the upper turn of the dynamic soaring cycle, a period previous thought devoid of flaps. These results also suggest possible sexual differences, where males seem to flap more often than females and limit their take-offs to favourable wind conditions. This study shows how multiple fine-scale loggers can be used to gain insights on how seabirds of varying body sizes are able to travel vast distances in the dynamic Southern Ocean environment. **Authors:** Stefan Schoombie¹, Rory Wilson², Peter Ryan¹ ¹FitzPatrick Institute of African Ornithology, ²Swansea University