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 opening line is abrupt, monosyllabic and emphatic. The reader may assume it’s a  metaphor , and attests to an obsession. Those readers familiar with the  Daedalus and Icarus  myth will immediately grasp the meaning; the recognition by the father of the significance of birds and the  foreshadowing  of the future disaster.
Daedalus