Bingo! I actually posted this on a new thread, having missed this one. It is a bird call, indeed, but I'm not familiar enough with the birds of the West to make a positive ID. As an East Coast birder, it sounds similar to the song of the Wood Thrush, a melodic forest dweller, but it's not an exact match. My guess- it's a reference to a place "where the birds sing a happy song, and there's music in the air," Twin Peaks or perhaps, the Black Lodge. But it's David Lynch, so your guess is as good as mine.