Behaviour as described does not seem really typical, but they can be in trees/shrubs - the photo suggests a bird at eye-level in some sort of creeper - looks ideal. Neither species is really very skulking.
If it did give a high-pitched Arctic-like call this might suggest Yellow-streaked, which reportedly calls like a bunting, but I've never heard it.
Bill looks fine enough but there is overlap I believe.
Mike Turnbull.
[ Last edited by tmichael at 17/11/2010 15:24 ]