When we come to consider the eastern birds, we have to distinguish between resident species and migratory ones. The Black-throated Thrush (_Turdus atrigularis_), which has been twice obtained in the British Islands, is a mere straggler to Europe, and is not known to breed there at all. Better known birds, perhaps, are the Golden Thrush (_Turdus varius_), which has even occurred as far west as Ireland, the Rock-Thrush (_Monticola saxatilis_) and the Scarlet Grosbeak (_Carpodacus erythrinus_), which breed in Eastern Europe, but are known only as occasional visitors in the west.
To judge by their distribution, the Bullfinches (_Pyrrhula_) are of Asiatic origin, for seven species out of ten are confined to that continent. Our common Bullfinch (_P. europæa_) probably came with the Oriental migrants, or perhaps its ancestors did. But the larger Northern or Russian Bullfinch (_P. major_) has no doubt entered our Continent directly from the east. We have in many groups similar instances of closely allied species or varieties, one of which, originating at a somewhat later stage than the other, took a different route of migration from that followed by its near relative.
The Pine-Grosbeak (_Pinicola enucleator_) is only known to British ornithologists as an exceedingly rare visitor. Its real home lies in the northern parts of Europe, Asia, and North America, and it is one of the most typical of the Siberian migrants.
But there are a number of other species of birds, which, though probably not of Siberian origin, only migrated westward recently, and have either not yet reached the British Islands, or which lead one to suppose, from their British range, that they are eastern forms.
Such, for instance, is the Nightingale (_Daulias luscinia_), which is probably of Oriental origin, but only visits England regularly in spring. There is no authenticated record of its ever having migrated either to Scotland or Ireland.
The Bearded Titmouse (_Panurus biarmicus_) is one of the eastern birds still resident in England, though unfortunately it seems to be on the verge of extinction. It is unknown in Scotland and Ireland. Another resident eastern species is the Nuthatch (_Sitta cæsia_), but neither of these is probably of Siberian origin.