LXXX 
BIRDS OF DUMFRIESSHIRE 
Mr William Evans, writing of the Fauna of the Forth 
Area states : " It is a feature of our bird-life for many 
species to be partially resident and partiaUy migratory. 
Thus while some of our Song Thrushes are resident all the 
year round, a large proportion are essentially only summer 
visitants ; others, again, visit us merely as birds of passage, 
and it may be that some play the part of winter visitants. 
Such cases, it will be seen, render satisfactory grouping 
difficult, and show the importance of the study of geo- 
graphical races."* The fact that certain species may be 
seen perenniaUy in a locality does not prove that the indi- 
viduals seen in spring are the same as those seen in wmter ; 
though, from the want of a better term, such species 
are classed as "residents." An annual emigration 
in reahty frequently takes place, and what wou d 
otherwise become conspicuous blanks in our bird-world 
are filled up by immigrants of the same species from 
elsewhere. Thus, though it may be that individuals 
in the middle zone are sedentary, it is expected 
that at the northern Umit of the distribution of a species, 
no birds of that species will be found in winter ; while 
conversely at the southern limit of its range no bird of that 
species will be found in summer. 
It would scarcely come within the scope of the present 
work to offer suggestions for the impulse and reason of 
migration. Wind and weather, high or low temperatures, at 
the time of migration, aU influence the actual dates of arrival 
and departure of the migrants; and "one thmg seems 
tolerably certain, and that is, such migration mornmgs m 
autumn always occur when the barometer is stationary 
or has just commenced to faU."t " In the sprmg time of 
the year, any mUd, moist, and therefore dark night, with 
not too strong a wind from any compass except the north, J 
is pretty sure to b^ utiUzed by the feathered immigrants. 
• Proc. Roy. Phya. Soc. Edin., Vol. XVII., p. 64. 
t Ann. Scot. Nat. Hist., 1903, p. 195. 
% Op. cit., 1903, p. 204. 
