This behavior is similar to bats as they approach targets. 새들은 또한 둥지에 접근할 때 주변 새들에게 방해가 되지 않도록 경고하기 위해 낮은 클릭음과 울음소리를 연달아 냅니다. It is thought that the double clicks are used to discriminate between individual birds.