If you must try for Saw-whets in winter, such as on a Christmas count, there are no good techniques. A few birders have heard birds tooting, or giving the "scree-aw" call. It wouldn't hurt to try a few calls, either by calling yourself, or with tapes. You have a very low chance of getting a response, but it certainly wouldn't hurt. The pine stands along the entrance road to the Bodie Island lighthouse has had a few birds in recent winters, though very few of the birds have been seen (possibly being "taped out" by over-frequent use of calls along this short stretch of road).