Range descriptions from Clements:
Great Gray Shrike, Lanius excubitor
*L. e. excubitor: W and n Europe to w Siberia
*L. e. homeyeri: Balkan Peninsula to s Ural Mountains and w Siberia
*L. e. leucopterus: W Siberia to Yenisey River

Northern Shrike, Lanius borealis
*L. b. sibiricus: E Siberia to n Mongolia and Kamchatka Peninsula
*L. b. bianchii: Sakhalin and s Kuril Islands (n Japan)
*L. b. mollis: Russian Altai and nw Mongolia
*L. b. funereus: W China (Tien Shan Mountains)
*L. b. borealis: breeds Alaska and northern Canada, south to extreme northern British Columbia and Alberta, northern Ontario, and Quebec; winters southern Canada and northern United States.

And for reference:
Southern Gray Shrike, L. meridionalis
*L. m. meridionalis: Iberian Peninsula and s France; > to nw Africa
*L. m. koenigi: Canary Islands
*L. m. algeriensis: Morocco (n of Atlas Mountains), coastal n Algeria and Tunisia
*L. m. elegans: N Sahara (Mauritania to Sinai Peninsula and Red Sea)
*L. m. leucopygos: S Sahara (Mali to Nile River valley of the Sudan)
*L. m. aucheri: W coast of Red Sea to s Iran and Arabian Peninsula
*L. m. theresae: Galilee hills of n Israel and s Lebanon
*L. m. buryi: Yemen; vagrant to Djibouti and Ethiopia
*L. m. uncinatus: Socotra
*L. m. jebelmarrae: W Sudan (Darfur)
*L. m. lahtora: E Pakistan and n India
*L. m. pallidirostris: Iran to arid steppes of w China (Xinjiang, Gansu and Ningsia)