I love the birds and other sound effects, it instantly paints this vivid, natural scene in your mind when you listen. The use of spacial sound is fantastic as well, as it really feels like it's all around you.
The xylophone (marimba?) almost sounds like it's clipping a bit to me, but it might just be some distortion you applied. Either way it adds a bit of grittiness to the otherwise rather tranquil, peaceful feelings of the other instruments.