Looking again at the Dunlin recovery map for JN69442, the straight line I added may help lead the eye to deepest Russia, but of course the bird wouldn't have actually flown that route. Chances are it hugged the mudflats along the North Sea and through the Baltic Sea. The Waddenzee is the Dutch name for a large intertidal zone in the south-east North Sea, running from The Netherlands through Germany and on into Denmark, now added to the map in red.
For readers who haven't come upon the Flyway concept before, migratory studies have revealed clear favoured routes for seasonal migrations between continents. The East Atlantic Flyway is the chosen route between high Arctic breeding grounds and Western Europe on into Africa.
Heading from Russia to overwinter in west/south-west Africa? No problem, skirt the edge of the Northern European Plain to the Waddenzee and beyond:
Maps of the Waddenzee, together with detailed species accounts covering nearly a quarter of a century, can be found in an excellent report available online- Trends of Migratory and Wintering Waterbirds in the Wadden Sea 1987/1988-2010/2011 (well worth a read, even though they only went and Anglicised the flippin' name!)