BIRDS. 
234 
in those notorious for similarity in certain points of 
structure and economy. In regard of migration 
this is especially evident, and this contrariety of 
action may at once be found illustrated in the in¬ 
congruity of the above assemblages, and still more, 
by comparing them with the remaining birds of the 
Devon list which are stationary, or nearly so. Some 
of the Warblers for instance are stationary, while 
the bulk are migratory, and the same remark applies 
to the Gull tribe. Again, individuals of some 
species are resident the year through, while the 
main body passes for a season to some other country, 
instanced in the Snipe and Chiff-chaff. 
In a former chapter I had occasion to observe in 
illustration of the effects of climate, that in 1837 
our spring birds of passage arrived late, apparently 
in consequence of a very backward season, or pro¬ 
tracted winter. In 1838, which w r as likewise 
remarkable for backwardness of its spring, I made 
the same observation on the vernal migrators, and 
have since found, that Mr. White in his Natural 
History of Selborne, in Hampshire, has recorded the 
sanje fact. See Part ii. Letters ii. and l. It did not 
appear however that all species were affected alike, 
for I noticed this late arrival only in the Swallow , 
Whitethroat , Fauvette and Cuckow , though had 
circumstances allowed me to have been more 
abroad I might have found that other kinds came 
under the same rule, at least in part. Weather is 
decidedly the most controuling influence on migra¬ 
tion, it not only affects the arrival of birds with us, 
but also their departures, since notwithstanding 
abundance of food, a summer bird of passage will 
quit us abruptly on the accession of inclement 
weather, and while early severity of winter weather 
obligates the polar migrators to leave their residences 
in the north abruptly, they likewise quit us late 
should the weather remain severe through a pro- 
