My son has birds in his head.
I know them now. I catch
the pitch of their calls. Their shrill
cacophonies, their chitterings, their coos.
This replicates the opening line, a refrain or  anaphora , the visual and poetic representation of the cage that encloses the birds that are Icarus. The reader knows that this cage will soon open and destroy the boy. 
 And so the poem ends, its sad tone and detachment a sign of Daedalus’s disappointment and grief at what will happen.
Daedalus