Geometry of a hawk's flight

One of the poets featured in the current Poetic Likeness Exhibit -- featuring photographs and paintings and sculptures of poets along with a few favorite lines -- at the National Portrait Gallery is Robert Penn Warren (1905-1989).   Although I hugely admire Warren's novel, All the King's Men, I am not very familiar with Warren as a poet.  The gallery posted, beside Warren's photo, a few lines about a hawk.  And I went searching online to find more.  The exhibit's quote was from Warren's "Mortal Limit" but my search led first to "Evening Hawk" -- with a first stanza bright with geometry;  I offer that stanza here.

       Evening Hawk     by Robert Penn Warren

       From plane of light to plane, wings dipping through      

       Geometries and orchids that the sunset builds,

       Out of the peak's black angularity of shadow, riding

       The last tumultuous avalanche of

       Light above pines and the guttural gorge,

       The hawk comes. 

       . . . .

The remainder of "Evening Hawk" and more by and about Robert Penn Warren may be found here at the Poetry Foundation Website.  
Also represented in the Portrait Gallery's poets' exhibit (which ends April 28) is Marianne Moore (featured in this March 21 post).