Choosing the route

Swallows fly to Africa for our winter

Migrating birds do not just point themselves in the right direction and hope for the best. Each species has its own traditional route.

Most routes follow obvious landmarks such as river valleys or coastlines. Some birds take winding routes around the coast. Others travel more directly, even if this means crossing perilous stretches of desert or sea. Routes often converge at certain junctions, such as mountain passes or narrow sea crossings.

Many migrating birds return along roughly the same route they followed on outward journey. Others return a different way, so their annual journey is roughly circular. This is called loop migration. 

Sand martins fly to Africa over the western Mediterranean, passing to the west of the Alps, but return in a loop via the eastern Mediterranean, passing to the east of the Alps. Loop migration allows birds to make use of food supplies or weather patterns that are found in different places at different times.