Swallows, together with martins, form a family of
passerine birds known as the Hirundinidae. They are found around the world on all continents, including occasionally in Antarctica. There are around 90 species of Hirundinidae, with the greatest diversity found in Africa, which is thought to be where they evolved as hole-nesters. For the most part swallows are
insectivorous, taking flying insects on the wing and using
foveae in their eyes to help track prey.
This picture shows the pied-winged swallow, which is found in several countries in western Africa.Photograph: Charles J. Sharp