Arctic tern flyways and the changing Atlantic Ocean wind patterns

Migratory bird trajectories are the result of their own speed and direction in combination with wind speed and
direction. Several studies have focused on the interplay between bird migration and general wind patterns,
however, the majority of them did not take into account climate change and used a small number of individuals.
By integrating tracking data from two populations of Arctic terns (n = 72) with ERA5 and Earth System Model
(ESM) wind data, we were able to study the current conditions and the potential effects of climate change on
them.
The Svalbard birds experienced wind support values around 3 m/s with a relatively low variability, while the
Dutch population experienced almost no wind support with a greater variability. Svalbard terns exhibited better
adjustment of their flyways to daily and annually varying wind conditions, and responded to crosswinds by
drifting over extended periods/regions (median Drift Ratio ± standard deviation: 0.51 ± 0.18) while the Dutch
population mostly compensated (0 ± 0.31). We suggest that the Svalbard birds will be able to adapt their flyways
to future Atlantic Ocean wind pattern changes, while we are uncertain whether the Dutch population can keep
compensating for future changes or not.
We examine the robustness of our results by using a selection of ESMs and by including metrics for several
uncertainty sources (ESMs, wind variability, tracking method etc.). This study highlights the importance of wind
as a flyway-shaping factor and points out the possibility for different responses to wind by different populations
of the same species, in different Ocean regions and seasons.