The fable is from the Chuang Tzu. This translation is from Arthur Waley in Three Ways of Thought in Ancient China, Anchor 1955)
There are birds that fly many hundreds of miles without stopping. Someone mentioned this to the cicada and wren. The two animals decided that such a thing was impossible. “You and I know very well that the furthest one can get, even by the greatest effort is that elm tree over there; and even then one can not be sure of getting there every time. Sometimes, one finds themselves dragged back to earth long before reaching that elm tree. All of these stories abut flying hundreds of miles at one stretch must be shear nonsense.
The cicada and the wren have valid experiences; their thoughts and imagination are shaped by these. Ultimately, their lives are confined by the imagination that comes from mistaking these experiences to be complete.
Life for the cicada and wren is as it seems. It is when the possibility arises, perhaps in a chance situation, that there is a world with potential never imagined. This can be the beginning of a search for the tools to go beyond the current experience.