Is it dead. Find it — Windhover

The key is "You or the Wind" in line four, a hunter and his windhover, a master and his bird that preys other birds. Dickinson's question to the bird, happy, conscious, homesick, is to accuse a black slave who helped his white master to press other slaves.

Is it dead－Find it－
Out of sound－Out of sight－
"Happy"? Which is wiser－
You, or the Wind?
"Conscious"? Won't you ask that－5
Of the low Ground?

"Homesick"? Many met it－7
Even through them－This
Cannot testify－
Themself－as dumb－
(F.434/J.417)
[1] it:: a bird hunted by a windhover; a slave escaped.
[2] sound, sight:: no trace of the prey; opinion and vision were not allowed for slaves.
[4] You:: a hunter. Wind:: windhover, a name for the kestrel, from its habit of hovering or hanging in the air with its head to the wind (OED); the image of hovering shows less labor required like a slave leader.
[3, 5] Happy, Conscious:: the two questions are suspicious.
[6] the low Ground:: the mean creature on the ground; an inferior foundation, indicating the slavery.
[7] "Homesick"?:: a windhover living with human; a slave far away from home.
[7, 8] Many, them:: other birds; other slaves.
[9] Themself as dumb:: birds that cannot speak; slaves who must keep silent.

KESTREL. WINDHOVER. It is easily reclaimed, and was taught to capture larks, snipes, and young partridges. It becomes very familiar when tamed, and will live on terms of perfect amity with other small birds, its companions. It formed, and perhaps still forms, one of the so-called 'happy family,' to be seen, or which was lately to be seen, in London. ─ A History of British birds (1851)