Merriam's Chipmunk (Neotamias merriami), Picchetti Ranch Open Space Preserve, Santa Clara County, California - July 2009. I found several of these chipmunks in an oak tree making loud and persistent vocalizations that sounded a bit like raucous Bushtits. Reportedly, these little sciurids can make sounds that mimic Northern Pygmy Owls, but I didn't hear those this time.