What is this instrument?

There was a musical composer on the radio this evening who seems to have made a musical composition out of bird song and accompanying natural noises.
First time I came across the concept (for a whole piece) but I wouldn't be surprised to learn that it was in fact a genre.
Sounded nice but I just heard the first ten seconds or so..

This little duet between wolf and alto-sax has always been one of my favorites.