Swallow is the general name of 74 species of birds of passerine family. Small shape, narrow wing tip, concave tail, short beak, weak feet, not too many feathers. The feather coat is monochrome, or blue or green with metallic luster; Most species are similar in both sexes. Swallows spend a lot of time catching pests in the air. They are one of the most flexible finches. They mainly feed on mosquitoes, flies and other insects. They are well-known beneficial birds. Nest in tree holes or cracks, ...