For Audubon, from Poem A Day, edited by Laurie Sheck, Volume 2 (2003). More on Robert Penn Warren here:
http://www.poetryfoundation.org/bio/robert-penn-warren
from VI Love and Knowledge (from Audubon: A Vision) / by Robert Penn Warren (1905–1989)
They cry
In a tongue multitudinous, often like music.