454 THE ZOOLOGIST. 
quarters, a corresponding change will take place in the dis- 
tribution of so-cailed “accidental occurrences” of continental 
species in Britain; and further, that this will be aided to a 
considerable extent by the northern range of such species on 
the Continent during the breeding season in exceptionally fine 
summers, or by the natural extension of the breeding haunts of 
many species. 
One more point I would like to bring forward in support of 
what I still consider theory, but which to me seems strongly 
supported already by known facts. In ‘The Field’ of May 7th, 
1881, were recorded occurrences of the Pied Flycatcher in 
Sutherland and Rosshire; and about the same date other occur- 
rences were recorded from various parts of the east coast of 
Scotland. A pair lingered a long time at one locality in East 
Sutherland, but finally disappeared. These, of course, belonged 
to the spring migration of 1881. Now, how are we indebted for 
such an unusual visitation so far west of the continent of Europe 
at this season? My idea—theory, if you will—is as follows :— 
As we have shown in our Report for 1880 that birds were carried 
farther west than usual by the easterly gales of the autumn of 
that year; the consequence of this was that the birds wintered at 
localities farther west than usual, and also returned to their 
breeding haunts by routes removed farther west than usual in 
the following spring. 
It may be said it is a pity to advance theories without sufficient 
bases of facts in such matters, and doing so might perhaps be 
characterised as unscientific; but I advance it in what I believe 
to be the interest of our enquiry, whether correct or erroneous; 
because what we want is more general attention to the meteoro- 
logical necessities of our investigation, and a wider appreciation 
by our reporters and those who are assisting us of the necessity 
of a comparison of the data, year with year, in the future. It is 
on this account that I would urge the mapping out of the dis- 
tribution of the occurrences of rare continental forms in Britain, 
year after year, and also the comparison of these annual maps, 
the one with the other, and with the meteorological facts of 
each year. 
Mr. J. J. Dalgleish and Mr. Freke are doing good work in 
enumerating all the occurrences of American birds in Europe 
and mapping them out, and vice versa. It would be desirable to 
ee 
