Maps of all tracks of individual male pectoral sandpipers that departed the area around Utqiagvik, Alaska in 2012 (n = 49) and 2014 (n = 36). Colour indicates wind support (in m/s; green for tailwinds and red for headwinds, see Methods for details). Tracks are shown as minimum convex polygons with 100 km spatial buffer (map scale lower right corner). White arrows at every fifth position indicate the current wind direction and wind speed, in m/s scaled by a factor of 10000), to increase visibility. The grey-blue area indicates suitable breeding habitat within the known breeding range of the pectoral sandpiper [27]. Map projection: polar Lambert azimuthal equal area with longitude origin 156.65° W (Utqiagvik) from Natural Earth (http://www.naturalearthdata.com). Below each map the following information is provided: ID, a combination of individual identity and “a” or “b” in case there is more than one track for an individual; Departure time, date and time of the first position of the track over the sea; Flight time, time from departure time until the last position over sea; Flight length, the distance covered between the departure and arrival points; Detour, detour in comparison to the shortest distance between the departure and arrival points; Track straightness, track length divided by the shortest distance between the departure and arrival location, a straightness of 1 indicates a direct flight between two points; Mean wind support (WS) and the mean wind support on the shortest route (shortest), the mean wind support during the flight at ~750 m altitude and the mean wind support the bird would have experienced had it taken the shortest route (see Methods).