a small black and white bird that comes to northern countries in the summer.——朗文当代大辞典

A bird of the genus Hirundo, esp. H. rustica, a well-known migratory bird with long pointed wings and forked tail, having a swift curving flight and a twittering cry, building mud-nests on buildings, etc., and popularly regarded as a harbinger of summer (cf. 1c).——牛津当代大辞典  @en