The sub species of Southern Grey Shrike on Tenerife is "koenigi" - known either Canary Islands Grey Shrike, or in some quarters as Desert Grey Shrike. The taxonomy of this latter group is complicated, with "elegans" and "algeriensis" also in the mix. "Algeriensis", as you might expect, is found in North Africa, but only on the coast, with "elegans" inland, and "koenigi" is restricted to the Canary Islands. The differences are not that clear, at least not to me, but the Canary Islands sub-species ought to have less white in the wings, and almost no super. Or at least that is the theory - I am not convinced!
So this bird here is interesting, as it doesn't show much white in the wing, but does have a fairly broad white supercilium - could it in fact be a stray "elegans" based on this feature? The final photo is of a completely different bird, but also exhibits a massively extensive white super. As before though, the white in the wing is limited.
To my knowledge I've not photographed "algeriensis", but did catch up with "elegans" in Morocco earlier this year. Take a look at the difference, I have to say I am confused as my inland Moroccan bird has to my mind significantly less iof a white supercilium than either of the birds on Tenerife. The final photo is of a different bird in the same area of Morocco, also exhibiting barely any white above the mask. Confused? I am!