Conversation so far:
what was birdsong and the 1960s by oliver messiaen?
While he had long been fascinated by birdsong, and birds had made appearances in several of his earlier works.
did he make any pieces based on birds?
Messiaen incorporated birdsong into all of his compositions and composed several works for which birds provide both the title and subject.

Question: which one of them was most known?
Self-contained rewrite: Which of Olivier Messiaen's compositions was most known?