Sanlian in Mandarin literally means “three together.” The islets are connected tightly to one another, although their shapes and colors are quite different. This makes Sanlian Islets geologically unique.
Many east Asian migratory birds stop by Matsu Islands. In May 2000, the Council of Agriculture included eight islands and reefs uninhabited by humans in Matsu as the Matsu Islands Tern Conservation Area - Shuangzi Reefs in Dongyin Township, Baimiao, Zhongdao, Tiejian, and Sanlian Islets in Beigan Township, Jinyu and Liuquan Reefs in Nangan Township, and Sheshan in Juguang Township. Seven bird species are currently under protection in the area: bridled tern, black-naped tern, roseate tern, greater crested tern, black-tailed gull, Pacific reef heron, and Pacific swift.