from South-east Russia to Turkestan in summer, and winters in Southern
Africa. This fact may possibly be due to two distinct migrations from
Asia having taken place: an earlier one from the South-east--that is to
say, an Oriental one--and a Siberian one more recently. In this case the
members of the two migrations have not become sufficiently
differentiated to be regarded as distinct varieties. Though most of the
Wagtails have a somewhat northern range, none (except perhaps _M.
borealis_) are truly Arctic; and indeed, as almost all of them pass the
winter in southern latitudes, it may be assumed that they are of
southern and not of northern origin.

The Dippers (_Cinclus_) are practically unknown in the Central European
plain, but they occur in Western Europe as far north as Scandinavia,
also in the Alps, Carpathians, and Southern Europe, including Sicily and
Sardinia. Some authorities distinguish three species, others only one.
As a matter of fact, the difference between the three forms is very
slight, and their nests and eggs are undistinguishable. Eight other
species have been recognised, and all these are either Asiatic or
American. As one of the American forms is peculiar to Peru and another
to Ecuador and Columbia, and since the genus as a whole is a
mountain-genus, it probably is an ancient one. Its European range alone,
however, implies that it has inhabited our continent for a considerable
time and is no new-comer. We may look upon it as of Asiatic origin. The
ancestors have spread east and west, the European species having arrived
with the earlier Oriental migrants, and wandered along the Mediterranean
at a time when the geographical conditions of that sea were vastly
different from what they are to-day.

Not quite so ancient as the Dippers, but likewise Asiatic in their
origin, are the Bullfinches (_Pyrrhula_). The closely allied
Pine-Grosbeak (_Pinicola enucleator_) has already been referred to (p.
191) as a member of the Siberian migration. The distribution of the
European Bullfinch (_P. europaea_) is very interesting, as it occurs in
two distinct forms, by some authorities regarded as races, by others as
species. In all probability these two races owe their origin to two
different migrations from the same ancestral stock. We may suppose that
_P. europaea_ came to Europe along with the Oriental migration, spreading
chiefly over the south and west, while another branch developed in
Siberia into the larger a