This time of year I always hear this PEEP in the woods that sounds similar to a spring peeper, but I just don't think it is one. I've heard tapes of night migrating thrushes making a similar noise, but the maker of this noise is not moving and I hear it in the day, not at night. I know peepers do peep in the fall or late summer, but I still think it's a bird.
Pretty sure I asked this same question last fall, and maybe the fall before that, and nobody answered, but trying again!
Lila