220 BIRDS. 
Fauna; it is for instance under this impulse that 
the Wild swan migrates in winter so far south as 
Devon, and the same cause sets in motion the 
generality of aquatic birds which usually are limited 
at that time to more northern stations in the Island, 
and compels them to seek food by roaming over 
the southern shores. Some unknown causes induce 
them however rarely to visit us at other seasons, 
both in the case of the inhabitants of high latitudes, 
and of our own English birds, witness the Northern 
diver and Crested grebe. The young only of some 
species of water fowl stay with us in winter, as 
happens with the Guillemot. On land, many kinds 
congregate during the cold season, and roam in- 
differently over the fields to procure food, as occurs 
with the Lark. The Chaffinch makes a more 
direct emigration southwards. The Missel thrush 
after the breeding time keeps its family together, 
and is seen in autumn traversing the orchards 
and gardens every where, feeding on ripened ber- 
ries and similar provender ; Gold-crests crowd 
much into orchards towards winter. The individu- 
als ofsome species influenced by some inappreciable 
cause remove from their more proper abodes, and 
are found with us under the title of straggling 
visitants, of which class the Black stork is an 
example. On the whole therefore as before said, 
the movements and migrations of birds are so 
manifold as to require an investigation of the habits 
of each species of bird respectively. The manner 
in which the question of migration is ordinarily 
treated is far too summary, and instead of ranging 
our migrants into three classes or kinds, we ought 
rather to reflect that each species is endowed with 
a separate instinct for its guidance and well-being 
in this respect, and that irregularities of action occur 
among even the individuals, of certain kinds. 
TF ie 
