You need to include:
-The main points of the poem and analyze what the main theme is (the moral or idea expressed in the story). This is the subject matter.
-Nature aspects in the poem that seem free or carefree (Like wind or open space). Then contrast them in comparison to being shut in a cage (enclosed, cramped, still, stuffy).
-The mood is how the reader feels. What does it make you feel? (Note: this is a literary element, which are classified under literary devices)
-The tone is how the author feels, what you think his/her mood is. (Also a literary element)
Put this in a short paragraph.