Second Sound: The Mystery Chirping!

After I sat by the intersection for a while I noticed a sound coming from the bushes off to my left. I walked closer to the noise and knelt down in the snow by a fence. There was some kind of creature hiding in there! Although I never caught a glimpse of it, it made a delightful kind of warble sound. Maybe someone reading this will be able to help me identify it! There was a lot of traffic and construction in area which can be heard in the background.

Listen to it here.

Here is a map of the site:


This is a photograph of the fence. Somehow that sign wasn't very intimidating: