Hi All -
The Northern Landbird Monitoring Program is run by University of Montana's Avian Science Center for the Northern Region of the US Forest Service (USFS) (which is described here: http://www.fs.fed.us/r1/ and includes the Nez Perce, Clearwater, and Panhandle NFs in Idaho). As part of this program a Flammulated Owl survey was initiated in 2005. More information and results for this survey can be found here: http://avianscience.dbs.umt.edu/research_landbird_flam.htm (information on related surveys can be found elsewhere on this web site).
The Nez Perce National Forest (headquarters Grangeville, ID) recorded the most Flammulated Owls of any of the Northern Region FS units surveyed with 69 detections out of 278 points surveyed (~21% detection rate). Some other interesting observations to come out of the survey as a whole are that birds were detected from May 9 to July 21 with detections only slightly lower after mid-June. Of all detections, 35% were of birds calling spontaneously before observers broadcast Flam calls.
This area has not been well known to Idaho birders as a place to look for Flams but clearly is. Parts of the Nez Perce NF are difficult to access and some distance from population centers but some of these areas should be fairly accessible. I was directed to one of the survey locations on the ridge between the Snake and Salmon Rivers near Lucille, ID several years ago and easily found Flams which responded readily to taped calls and were easily spotlighted as well (unfortunately this area burned last summer which may have displaced Flams from this area).