In December 1912 a South African farmer caught a barn swallow in his house. The swallow was wearing an engraved metal leg ring, placed there 18 months before by an ornithologist in Staffordshire, UK, when the bird was just a chick in its nest. This was the first incontrovertible evidence that barn swallows migrate from Europe to southern Africa.
Today, we know that more than five billion birds, representing about 200 species, travel between western Eurasia and Africa each year. They indude waders and wildfowl, raptors and songbirds, doves, owls and storks. Some travel slowly with many stops, others undertake epic non-stop flights. Some fly by night and some by day, some en masse and some alone. The common thread is that they breed in the temperate spring and summer of Europe, when food is abundant and temperatures kind, but leave before winter arrives.