Every spring, various migratory bird species return to their breeding grounds all over Europe, as far as the wild geese in Scandinavia and northern Siberia or much closer to the Mediterranean. Even at the shortest passages, the Gibraltar Strait and the Marmara Sea, gliding many miles without soil is perilous, but so are predators all along each route, like the peregrine falcon. Some (stork) nests are family heritages for many generations. Human landscape changes, such as urbanization, significantly change conditions. Navigation is by astronomy, earth magnetism and landmarks.
—KGF Vissers