Nice explanation from Charlie. I would add a twist from the psyche point of view : if : "birds' are persons or idea If: "bright feathers" means power, energy radiating from them. So you can see the meaning as: "you simply cannot stop powerful idea " or "you if you cage a bright mind, you will loose it's potential "

I suppose this means that: 1 - there is a lot of beauty to be found in nature 2 - the best place to find the beautiful creations of nature is in their natural habitat 3 - therefore, putting search creations in an unnatural habitat, such as a cage, is undesirable However, I think it is ridiculous to suggest that just because one part of the natural world is more "beautiful" then another, this this feature should guide us as to whether or not we we put it in a cage. This sounds like racism applied to the the "natural world".