In the clear sky, there is a crane on the clouds. Why use one instead of group?

1. The ancient word "one" does not just refer to quantity. A crane does not refer to one crane, but can refer to a group of cranes in the poem. Therefore, the meaning of a group is already included in it, and it also depicts the formation of cranes in the sky. It can be said that one word has multiple meanings. It is more vivid and has deeper meaning than "group of cranes". 2. It is the need for rhyme.