The barn swallow (Hirundo rustica) is the most widespread species of swallow in the world. It appears to have the largest natural distribution of any of the world's passerines, ranging over 251 million square kilometres globally. It is a distinctive passerine bird with blue upperparts and a long, deeply forked tail. It is found in Europe, Asia, Africa and the Americas. In Anglophone Europe it is just called the swallow; in northern Europe it is the only common species called a 'swallow' rather than a 'martin'. There are six subspecies of barn swallow, which breed across the Northern Hemisphere. Four are strongly migratory, and their wintering grounds cover much of the Southern Hemisphere as far south as central Argentina, the Cape Province of South Africa, and northern Australia. Its huge range means that the barn swallow is not endangered, although there may be local population declines due to specific threats. (Source: Wikipedia.org, CC BY-SA)