Flyways of Common Cranes Grus grus breeding in Fennoscandia

Knowledge of migration patterns plays an essential role for understanding spatiotemporal distribution of birds. Here we used >15,000 sightings of 1,473 colour-ringed Common Cranes Grus grus to study migration patterns of birds breeding in five regions along a longitudinal gradient of Fennoscandia. Our results confirm that Fennoscandian cranes mainly use either a Western European flyway (W-flyway), to winter mainly in France or Spain, or a Central European flyway (C-flyway), to winter in Hungary or Israel. Finnish cranes showed the greatest variation in migration patterns in terms of distance and direction and only Finnish cranes were recovered in Africa. Many of the Finnish cranes, starting along C-flyway change to the W-flyway and winter in SW Europe or NW Africa. On the other hand, the Scandinavian cranes are rarely observed along the C-flyway. However, substantial numbers of cranes from NE Sweden cross the Baltic Sea and migrate via Finland but then follow the W-flyway from Germany and southwards, especially during autumn. These results can be used for conservation and management, e.g. to coordinate monitoring. They are also relevant for land use planning, e.g. to avoid windfarms at sites important for migrating soaring birds while crossing seas, so-called ‘thermal bottleneck sites’.