Here's another ornithological-musicological resource: Robert Fallon has got hold of several of Messiaen's field recordings of birds and compared them with corresponding passages in Oiseaux exotiques. Fallon estimates that "Messiaen's pitches are about 66% true to his models." His essay on the subject will appear in Christopher Dingle's forthcoming collection Olivier Messiaen: Music, Art, and Literature.
