燕子 (yànzi), or swallows, are small birds known for their graceful flight and distinctive forked tails. They are often found in various habitats, including urban areas, fields, and near water. Swallows are migratory birds, traveling long distances between their breeding and wintering grounds. These birds primarily feed on insects, catching them in mid-air. Swallows are recognized for their social behavior, often seen in flocks during migration. They build mud nests, typically under eaves or cliffs, and are known for their strong pair bonds during the breeding season.