Fig. 5
From: The use of nocturnal flights for barrier crossing in a diurnally migrating songbird
Windroses of the frequency of wind speeds at departure points for purple martins that either crossed (a) or detoured (b) around waterbodies (left in each panel). Corresponding histograms of flight directions from GPS tracked individuals (right in each panel). Bars on all plots indicate the directions that wind or flights are moving toward: winds during both crossings and detours flowed predominantly toward the southwest, and bird flights were directed predominantly toward the northwest (crossings) and west-southwest (detours)