PALLAS'S GREY SHRIKE. 597 



birds appear to have become so far differentiated as to have lost the 

 power (or at least the desire) to interbreed. In South-east Russia the 

 ranges of the White-winged Grey Shrike and of the Great Grey Shrike 

 impinge ; and on the Lower Volga by far the greater number of exam- 

 ples are intermediate forms between them which have been described 

 as a new species under the name of Lanius homeyeri, and which occur 

 sparingly in Siberia. There is every reason to believe that these inter- 

 mediate forms are the result of interbreeding. If this be so, we have the 

 interesting fact that, whilst the two extreme forms L. major and L. leuco- 

 pterus are so different that they no longer interbreed and are therefore 

 specifically distinct, they both interbreed with the intermediate form 

 L. excubitor, which is therefore only subspecifically distinct from either of 

 them. Curious as this mutual relationship of these three Grey Shrikes 

 is, many explanations might be easily imagined. The probable one is, 

 that the Grey Shrike which inhabited the Palaearctic Region before the 

 Glacial epoch was during that period driven southwards and isolated in 

 three colonies one in South Europe, one in Turkestan, and one in 

 Eastern Mongolia. The difference produced directly or indirectly from 

 the change in the surroundings seems, in this instance, to have been 

 somewhat similar to what appears to be the rule in the variations in birds 

 which extend across the Palaearctic Region. The western form varies 

 considerably from the central form; but in the east, instead of the 

 variation increasing, it diminishes, and the western form reappears with 

 comparatively slight modifications. After the passing away of the ice, 

 the central colony, L. levcopterus, does not seem to have spread north- 

 wards again to any great extent ; but the other two colonies appear to 

 have extended their ranges round it, until they met somewhere near the 

 Ural Mountains. 



Of the habits of Pallas's Grey Shrike little can be said. They probably 

 do not differ materially from those of its near allies. As I travelled along 

 the banks of the Yenesay from Yenesaisk to Krasnoyarsk and across 

 country to Tomsk, Grey Shrikes were very abundant ; but it is difficult 

 to say to which species they belonged. I had no opportunity of shooting 

 any ; but as the skins sent me since from this locality belong to both 

 species, I probably saw both. They were very conspicuous birds, often 

 perched on the extreme summit of a small tree, and extremely fond of the 

 telegraph-posts and telegraph-wires. 



Of the nest and eggs of Pallas's Grey Shrike nothing definite appears 

 to be know}*. 



The thoroughbred adult male is a handsome bird, differing from the 

 Great Grey Shrike in having a white rump and with the white bases of 

 the primaries of less extent than in that bird, whilst the white bases of 

 the secondaries are altogether absent. 



