| 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 oceur 
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 Palearctic 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 
Kastern 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 Palearctic 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. leucopterus, 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 thé 
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 known. 
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. 
