High up in Si-yuan Pass, some time in late spring or early summer, you see a crested serpent eagle perched high up in a tree, while a white-faced flying squirrel peers dartingly left and right from the branches of a may chang tree. Down below, a rough-skinned toad deftly camouflages itself against a rock. Little wonder that Si-yuan Pass is dubbed a “ treasure trove of plant and animal species. ”
春夏之際的思源埡口，大冠鷲昂立枝頭，山胡椒樹前張著大眼睛左右顧盼的是白面鼯鼠，還有一隻盤古蟾蜍藉自己岩石般的粗糙皮膚隱身一角，無怪乎思源埡口被稱為「物種的百寶箱」。