12 NOTES ON THE BirRDS OF DUMFRIESSHIRE. 
may be described as almost periodic. The numbers of our 
annual immigrants are often alleged to he influenced by 
climatic conditions. It has been suggested that the occa- 
sional irruptions of Sand Grouse and Crossbills are due to 
overcrowding at the normal haunts of those birds. The 
scarcity of such species as the Swallow or the Land-Rail, or 
of our Barn Owls or Ring Ouzels locally, may at times be 
patent and is attributed to one reason or another but to none 
satisfactorily. Whatever the cause, I feel sure that if it were 
possible to take an annual census of Birds visiting, or resident 
in, any given area it would eventually be found that the num- 
bers vary far more than is generally supposed; not decade by 
decade or year by year, but from time to time. There are so 
many factors which influence bird-life that variation in num- 
bers is inevitable and one malignant circumstance may be 
ruinous. It has always seemed strange to me that in spite 
of all the investigations into the life-history of Birds so little 
should have as yet been done as regards the diseases of Wild 
Birds. I should not be surprised, when this subject comes 
to be studied scientifically, to learn that disease is the prime 
factor which controls the ups and downs of our Bird popula- 
tion to which I have referred. 
Had I drawn on my note-books so as to include 
ornithological records from the whole Solway area I could 
have made this paper considerably longer and more widely 
interesting : I have, however, confined myself strictly to the © 
County of Dumfries. Many of the observations now made 
should be compared with statements I have already published 
and the whole paper should be considered in conjunction with 
my Birds of Dumfriesshire published in 1910. I have adhered 
to the ornithological arrangement therein adopted and have 
avoided the vexed question of scientific nomenclature. I 
should perhaps add that, although I hope I have succeeded in 
gathering together all the items of interest as regards our 
local birds up to date, I have not attempted to modernise such 
information as I gave in 1910 concerning the distribution 
extraneous to Dumfriesshire of our visitors and visitants. 
The page references throughout are to my original book 
