CHAP. Il.] BIRDS. 19 
immediately connected with the process of reproduction. Some, 
as the salmon, enter rivers; others, as the herring and mackerel, 
approach the coast in the breeding season; but the exact course 
of their migrations is unknown, and owing to our complete 
ignorance of the area each species occupies in the ocean, and the 
absence of such barriers and of such physical diversities as occur 
on the land, they are of far less interest and less connected with 
our present study than the movements of birds, to which we 
shall now confine ourselves. . 
Migrations of Birds.—In all the temperate parts of the globe 
there are a considerable number of birds which reside only a 
part of the year, regularly arriving and leaving at tolerably fixed 
epochs. In our own country many northern birds visit us in 
winter, such as the fieldfare, redwing, snow-bunting, turnstone, 
and numerous ducks and waders; with a few, like the black red- 
start, and (according to Rev. C. A. Johns) some of the woodcocks 
from the south. In the summer a host of birds appear—the 
cuckoo, the swifts and swallows, and numerous warblers, being 
the most familiar.—which stay to build their nests and rear their 
young, and then leave us again. These are true migrants; but 
_ a number of other birds visit us occasionally, like the waxwing, 
the oriole, and the bee-eater, and can only be classed as 
stragglers, which, perhaps from too rapid multiplication one year 
and want of food the next, are driven to extend their ordinary 
range of migration to an unusual degree. We will now endeavour 
to sketch the chief phenomena of migration in different 
countries. 
Furope.—It is well ascertained that most of the birds that 
spend their spring and summer in the temperate parts of Europe 
pass the winter in North Africa and Western Asia. The winter 
visitants, on the other hand, pass the summer in the extreme 
north of Europe and Asia, many of them having been found to 
breed in Lapland. The arrival of migratory birds from the 
south is very constant as to date, seldom varying more than a 
week or two, without any regard to the weather at the time; 
but the departure is less constant, and more dependent on the 
weather. Thus the swallow always comes to us about the middle 
