Nice mood. The whistling and humming are a good addition to the feeling of a carefree climb, I appreciated them. Nice bending too, it makes me feel as if the climb is surely a nice time, but not effortless. I was a bit disoriented by the very first bend, maybe it's a bit weird to have it as the very first (actually second), isolated sound in the track. But it might be really subjective.
Nice work :)