sing是指唱歌，鸟儿鸣叫
例句
1.
If the birds have not flown for three years, they will soar into the clouds. If they have not sung for three years, their songs will take everyone by surprise.
三年不蜚，蜚将冲天；三年不鸣，鸣将惊人。
2.
A pair of orioles sing amid the willows green.
两个黄鹂鸣翠柳。
