ON THE MIGRATION OF BIRDS. 465 
plained in their proper place, there are immigratory and emigratory 
movements simultaneously observed on our coasts, the former affecting 
the east coast line only. 
Winter Movements.—In NovEeMBER, and not later than the middle of 
the month, the ordinary autumnal southward movements on the part 
of birds of passage and of British emigrants cease. 
These normal seasonal movements are followed later in the month by 
emigratory movements of a very different nature, and entirely due 
to a decided fall in temperature, usually in the form of outbursts of: 
frost, and to snow. These conditions drive certain species specially 
affected either to warmer districts within the British area, or to southern 
regions beyond our shores. Such movements as these naturally become 
more pronounced as the winter advances, and especially so during severe 
seasons. They are repeated during each cold spell in the months of 
DECEMBER, JANUARY, FEBRUARY, and in some exceptional seasons as 
late as the third week of Marcu. 
As soon as frost sets in, particularly if accompanied by snow and 
sleet, even if it is only locally diffused, it causes an immediate rush to 
the coast and its adjacent islands, especially to the western seaboard and 
to Ireland, where a milder climate usually prevails. 
The appearance of these birds on the coast in the late autumn and 
winter has led them to be regarded as immigrants from abroad. But 
when the whole of the data relating to their distribution is examined, 
the true nature of these movements is no longer doubtful ; and this is 
the case quite apart from the weather conditions, which, in all instances, 
also afford an unfailing clue to their true character. 
If the cold is very severe and prolonged, the isles off the south- 
west coast, such as Scilly and those off the west coast of Ireland, are 
sought, and many birds are observed at the southern stations to quit 
both Britain and Ireland. At such times these great western movements 
form the most prominent feature of the winter migratory records. 
In the terrible DecemBer of 1882, even these usually safe western 
retreats failed the refugees, and many succumbed, the hardy Snow Bunt- 
ing perishing along with the rest. The Januaries of 1881, 1885, and 
1887 were also very severe, and were months of great cold-weather move- 
ments. In 1881 many birds died of starvation at Valentia, then the 
least cold corner of the British area. 
During exceptionally severe winters there is a renewal of immigratory 
movements from the continent by way of the East and West Route across 
the southern portion of the North Sea. On arriving on our south-eastern 
shores the Larks, Starlings, Thrushes, and Lapwings, which are the species 
recorded, move along the south coast of England, and probably seek the 
warmth of the South-west, the Scilly Isles, and Ireland. 
The species which appear to be specially susceptible to cold, either 
constitutionally or through deprivation of food (most probably the latter), 
are the Mistletoe Thrush, Song Thrush, Redwing, Fieldfare, Blackbird, 
Greenfinch, Linnet, Starling, Lark, Water Rail, Lapwing, Curlew, Snipe, 
and Woodcock. 
In mild winters the only movements recorded are a few local 
migrations, which strictly coincide with the occasional periods of cold 
from which hardly any season is entirely exempt. 
Cold-weather migration is performed during both the night- and day- 
time. ae the flight is an extended one it is probably undertaken at night, 
: HH 
