Conversation so far:
what was the birdsong in relation to Olivier Messiaen?
Olivier Messiaen had long been fascinated by birdsong, and birds had made appearances in several of his earlier works.
Did Olivier Messiaen make any music pieces based on birds?
Olivier Messiaen found birdsong fascinating, notating bird songs worldwide and incorporating birdsong transcriptions into his music.
Which one of Olivier Messiaen's music pieces based on birds was most known?
Olivier Messiaen’s magnum opus was Catalogue d’Oiseaux (Catalogue of Birds), a work for solo piano completed in 1958.

Question: What instruments were used in the work?
Self-contained rewrite: What musical instruments were used in Olivier Messiaen's Catalogue d'Oiseaux?