What does the word "rung" mean in the poem "The Windhover," in the stanza

I caught this morning morning's minion, king
-dom of daylight's dauphin, dapple-dawn-drawn Falcon, in his riding
Of the rolling level underneath him steady air, and striding
High there, how he rung upon the rein of a wimpling wing

A. A rounded crosspiece between the legs of a chair

B. A heavy staff of cudgel

C. A spoke of a wheel

D. A high level of hierarchy