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516 
NATURE 
-[Marcu 31, 1904 
legislature to wake up and appreciate the fact that we 
must, by all legitimate means, encourage the estab- 
lishment of new industries within this realm? 
Ivan LEvINSTEIN. 
BIRD MIGRATION IN GREAT BRITAIN AND 
IRELAND. 
ae 
E great inquiry on the migration of birds as 
observed in Great Britain and Ireland instituted 
in 1880 by the British Association was brought to a 
conclusion at the Southport meeting last year, and it 
may be useful to describe shortly what it accomplished, 
and to direct attention to some of the results, which 
practically remain unknown except to a few orni- 
thologists specially interested in the subject. 
For eight years, 1880-1857, the committee appointed 
collected voluminous observations from the numerous 
light stations, some two hundred in number, around 
the British and Irish coasts. From the enormous 
amount of material thus amassed, a digest of the 
observations was prepared and presented to the Liver- 
pool meeting, and was published in the report of the 
Association for 1896 (pp. 451-477), affording, in a 
highly condensed form, the general results of the 
inquiry in all its aspects, geographical, seasonal, 
meteorological, &c. This was followed by a series of 
histories wherein each and every movement (and the 
very varied conditions under which they are per- 
formed) of eight birds carefully selected so as to in- 
clude every type of British migrant was exhaustively 
treated. 
These histories appeared in the reports for the years 
1900, I90I, 1902 and 1903. 
Turning now to some of the special results of the 
inquiry, in the first place it was clearly proved that 
a considerable proportion of our native-bred song 
thrushes, blackbirds, skylarks, starlings, rooks, lap- 
wings, and other species which are usually regarded | 
as being wholly resident throughout the year are 
migratory; indeed, they are as essentially summer | 
visitors to our isles as the swallow and the cuckoo. 
They leave us before the end of summer for southern | 
Europe, and are the first harbingers of spring to 
appear on our shores, arriving during February and > 
early March. 
As regards the geographical aspect of the subject, 
perhaps the most interesting of the varied movements 
investigated, if not actually discovered, are those re- 
markable intermigrations which take place between | 
the south-eastern coast of England and the opposite 
shores of the continent by a westerly autumn and 
easterly spring flight. Day after day in late 
September and during October, when the weather is 
suitable, vast numbers of  skylarks, starlings, 
chaffinches, tree sparrows, rooks, and jackdaws rush 
across the southern waters of the North Sea, proceed- 
ing chiefly due west off the mouth of the Thames (the 
centre of the stream), south-west off the coast of Kent, 
north-west off Norfolk, and north-north-west off the 
Humber. Corresponding return migrations, in oppo- 
site directions, are witnessed in the spring. A note- 
worthy feature of these movements is that they are 
performed during the daytime; indeed, they are the 
main diurnal flights observed on the British coasts. 
During the preparation of the digest and of the 
various reports, I was so much impressed with the 
singularity and importance of these movements that I 
decided to make some further investigations regarding 
them, and to this end I spent nearly five weeks on the | 
Kentish Knock light vessel, situated thirty-two miles 
east of the Essex coast and out of sight of land, during 
the past autumn (see Ibis, pp. 112-142). I was 
previously uncertain as to whence came these hosts of 
migrants, now I am of opinion that they are emigrants 
NO. 1796, VOL. 69] 
| 
| lands. 
from western central Europe, which, having probably 
descended the Maas, Rhine, and Schelde, quit the Dutch 
coast at the mouths of those rivers en route for winter 
quarters. Some of these remain during the winter in 
England, others proceed to Ireland, and others, again, 
depart from our southern shores for more southern 
There can be little doubt that many of those 
which remain in our islands winter in latitudes north 
of their summer homes ! 
Turning next to the meteorological aspect of bird- 
migration, it has been possible to make a careful 
comparison between the unique data obtained through 
the inquiry and the reports issued by the Meteorological 
Office, and thus to establish satisfactorily certain re- 
lations between migrational and meteorological pheno- 
mena, For instance, it has been found that each 
great arrival on our shores of migrants from north- 
west Europe in the autumn is correlated with a certain 
type of pressure distribution which establishes fine 
weather over the North Sea between Scandinavia and 
the British Isles. Such conditions, however, though 
they may prevail at the all important point of de- 
parture, and hence induce migration, do not always 
extend so far as Britain, and when this is the case 
the migrants pass into more or less unfavourable 
weather ere they reach our shores. 
During a month’s sojourn in the Eddystone Light- 
house (see Ibis, 1902, pp. 246-269) in the autumn of 
1got, I paid special attention to the weather conditions 
under which the migrants set out to cross the Channel. 
I found that no movements were witnessed when the 
weather was in the least degree unfavourable for the 
passage, and that the wind is undoubtedly the main 
factor in migration meteorology. The direction of the 
wind was of no moment, for the birds flitted south- 
wards in winds from all quarters. It was otherwise 
when its velocity came to be considered, and no 
movements were performed when this exceeded about 
28 miles an hour. At 34 miles the few stragglers 
Observed were in distress, and the only birds moving 
when it exceeded this and approached 4o miles were 
swallows and martins. My subsequent experiences at 
the Kentish Knock Lightship confirmed these con- 
clusions. 
The supposed influence of the direction of the wind 
on migratory movements has been much misunder- 
stood, chiefly because the dependence of the wind upon 
| atmospheric pressure does not appear to have been 
taken into consideration. We now know that certain 
types of pressure distribution are favourable for and 
conducive to migration, and the winds also resulting 
therefrom have erroneously come to be looked upon as 
the cause for such movements. 
Finally, the investigation of certain movements, 
namely, the emigrations, has presented exceptional 
difficulties, due chiefly to the fact that they are 
habitually performed under conditions which enshroud 
them in all but complete obscurity, indeed, often in 
complete obscurity. The reason for this is that, with 
few exceptions, emigration is undertaken during the 
hours of darkness, and thus entirely escapes notice at 
the place of embarkation. It was with the object of 
investigating this phase in the phenomenon of migra- 
tion that led me to visit the Eddystone, where it was 
possible to observe these emigrants immediately after 
their departure from our shores. There I found that at 
least go per cent. of the various emigrants crossed the 
Channel during the night. Indeed, night movements 
are undoubtedly the rule when considerable expanses 
of sea have to be traversed. To this rule the chief 
exception has already been mentioned; but both at the 
lighthouse and at the lightship I found that day migra- 
tion was confined to a few species only. 
Ws. EaGLe CLARKE. 
