Beethoven was far from the first to imitate birds in music. See, for example, _En ce gracieux tamps joli_ by the late-14th-century composer Jacob Senleches. I think what Sir Simon meant was that Ravel was among the first to use more precise transcription of birdsong, i.e. more than flute trills or imitations of cuckoos. This approach of course reaches its apotheosis with Messiaen.
