In the winter the park seems that much quieter, that much more remote and that much more wild. As such the sounds seem that much more vivid.
While I would not consider myself a birder by any stretch of the imagination, I have always stopped to listen to their amazing songs. My identification skills are poor at best, but in the spirit of learning a bit, I did some research on the web, and came across the following site that I thought I would share. It's named "All About Birds."
It's well worth a look, and includes some great audio clips of some of the marvelous sounds that the park has to hold.