BIRDS. 223 
exactly the causes of its extent in the ornithological 
department, and it is here only requisite to remark, 
that our eligible position towards several portions 
of the ocean, and several islands, and our proximity 
to the Continental States, ought to be taken greatly 
into account from the advantages these circum- 
stances afford in augmenting the variety of the 
pelagic birds. 
From the study of birds may be derived a most 
useful lesson to the naturalist. | Animals so high 
in the scale of intellect can hardly execute so many 
subtle actions and so many deviations from what 
we regard as their more positive instinctive tenden- 
cies, without furnishing information regarding the 
sources whence these actions spring. We find 
some birds penetrating southwardly in the winter, 
in proportion to the severity of the season, the 
Wild goose for instance ; we find some kinds in- 
cited to migration from their summer abodes only 
if the weather be very severe as seenin the Wild 
swan ; we find numerous cases where individuals 
alone choose in some years to emigrate, the main 
body of the species remaining stationary in its own 
proper country, instanced in the Red-tailed warbler, 
a native of southern Europe; we find cases of an 
opposite kind where the main body invariably 
migrates, some few individuals choosing to remain 
stationary, witnessed by the Gray wagtail, which 
occasionally stays in Devon to nestle, and rear its 
young; we find instances of birds which ordinarily 
appear here in summer, arriving at times in winter, 
(though this is a very rare fact) and vice versa of 
birds which generally come in winter, arriving in 
the height of summer, (an extremely common fact) 
