Northern Shrikes

Just when  I thought I'd safely categorized Shrike--versus Northern Mockingbird--I find that I am in the range of Northern Shrike instead of Loggerhead and they're not the same!  At home in Tucson, we're in the range of Loggerhead Shrike--only--but now that we have crossed the international border to the north, we are in the land of Northern Shrike and my learning has to expand, eh?
On a first glance the two Shrikes are pretty similar--and I may be forgiven for enthusiastically calling "Loggerhead" upon our arrival in BC.  The silence from my driving companion--a veteran birder of thirty-five years--assured me that I had made a mistake.  I looked again (in fact I turned around and stopped the car) and observed the bird more closely, that is I stared at the head.  The head appeared to be rounder than usual and the eye mask was rather limited--projecting only behind the eye and not extending across the forehead.  Also, this bird had a white forehead where the Loggerhead has a black one--a distinctive feature, IF you can see it.
So, it's not much to go on--both Shrikes perch in similar locations and both sound--at least to me--similar, but if you pull over and gaze next time you're in the presence of a Shrike, the chances are you'll get it down to species as long as you're in Arizona or British Columbia, and as long as you're not witnessing the first record of Brown Shrike in BC!