Through the course of the poem, the speaker spends a substantial amount of time describing a complex self. For instance he says:
Do I contradict myself?
Very well then I contradict myself,
(I am large, I contain multitudes.)
The poem continues with Whitman being accused of talking too much. He says:
The spotted hawk swoops by and accuses me,
He complains of my gab and my loitering
Whiteman feels as if him and nature are intertwined. This is why the connection between him and the hawk is so strong. He is intertwined with nature and nature is intertwined with him. However, he feels as if he is indistinguishable from the universe.
I too am not a bit tamed, I too am untranslatable, I sound my barbaric yawp over the roofs of the world
The speaker sees his self in the hawk as “untranslatable” being that we cannot understand the hawks language we define it as abnormal. What Whitman is trying to conclude is that “self” cannot be defined.

Earlier on in the poem he mentions that he does not ask the wounded person how he feels instead he becomes the wounded person. He vows to never translate self at all. From my understanding Whitman is trying to say what may be normal to me; may not be normal to someone else and versa. Therefore we are all untranslatable self, we can understand our self but someone else may not.