migratory bird; bird of passage
Refers to birds that migrate seasonally. The term is somewhat formal or literary; in everyday conversation, 渡り鳥 (わたりどり) is more common.
Swallows are migratory birds that come to Japan in spring.
この湿地は多くの候鳥の休息地になっている。
This wetland serves as a resting place for many migratory birds.