MIQEATIONS OF EUROPEAN BIRDS. 
327 
in Britain^ whilst the majority move southwards ; not so with 
their close ally_, the whin-chat^ which disappears entirely during' 
the cold season_, and^ with the migratory portion of the last- 
named species_, seeks the more genial climates of North Africa. 
Thus_, in all probability^ there are individual stone-chats that 
have alternately braved the cold of the north and the more 
cheerful winter of the Sahara; for we cannot suppose that 
there is a set that invariably stop in the north_, and another 
that constantly leave at the approach of winter. At all events^ 
here is displayed a flexibility of constitution often considered 
characteristic of man alone. Although the regular birds of 
passage maintain much exactitude with reference to their 
arrivals and departures^ others seem to err greatly when com- 
pelled by weather or other causes to trust to their own intelli- 
gence in guiding them from place to place ; even many 
migratory species far exceed the bounds of their usual resorts^, 
and certain individuals^ not known to be migratory have found, 
their way across the whole continent of Europe. A good 
example of the latter is seen in the late irruption of Ballasts, 
sand-grouse from north-western Asia^ so well illustrated by 
Messrs. Moore and Newton_, in the Ibis.'’^ The short- 
toed lark seldom migrates beyond the northern shores of 
the Mediterranean^ yet flnds itself often in Britain_, and. 
caught either in gales_, or wandering unknowingly north- 
wards ; occasional individuals of the Egyptian vulture from 
Spain^ the Grifibn vulture and spotted eagle from the- 
mountains of Central Europe^ and the spotted cuckoo from 
North Africa. Moreover^ several American species have been 
recorded_, chiefly water birds^ which^ of course_, are better 
adapted to brave the dangers of the deep. Certain birds — to 
wit^ the redbreasE song-thrush, and blackbird — do not leave 
the north of Europe, whilst many of their brethren of Italy 
and the neighbouring countries make regular annual migra- 
tions to Africa and the islands. To account for this remark- 
able anomaly, it will be observed that the robin of the south 
is far less omnivorous than its northern compeer, and is not 
nearly so familiar in its habits — like the warblers, it depends 
almost entirely on insect food ; consequently, when that fails, 
it has no alternative but to push southwards, and participating, 
like other species, in climatic effects, it would doubtless follow 
a like route ; and much the same with the thrushes, as they 
depend in a great measure on fruits for their winter subsistence. 
When the grapes of the south are gathered, having no holly- 
berries, mountain ash, or haws to draw on for their winter wants, 
they would naturally disperse ; probably many fly northwards as 
well ; for all the thrushes that cross the Mediterranean during 
winter are but an inflnitesimal part of what frequent Italy 
and the south of Europe in summer. No doubt much depends 
