xIV MIGRATION 351 
the Swallows will collect together and suddenly vanish, 
leaving behind them one or two of their number, who 
may or may not find their way to the far south where 
their winter should be passed. Even the caged bird, if 
a migrant, catches the fever and frets impatiently in 
his prison. It is said that a Brent Goose confined in 
a yard and longing for his arctic haunts, has been 
known in spring to migrate from the southern to the 
northern side of his narrow confines. Winter brings 
with it the Snipe, the Woodcock, the Fieldfarc, 
Redwing, and many others that come from the north 
to spend the cold season in our comparatively genial 
clime. All this is evidence, if we only think of it, of 
the most marvellous facts. That a Chiffchaff, whose 
daily occupation for months has been to pick grubs 
from the trees, and who has never left his favourite 
wood, should suddenly, some evening, be seized with 
an uncontrollable impulse to start for North Africa, is 
surely matter for wonder. Still more astounding is it 
that the young birds; with defective strength and no 
experience, should start on the great pilgrimage 
alone instead of waiting for the old birds to guide 
them. And in spring, too, when you see the first 
swallow, it is a startling thought that the small bird 
whom you see practising his short swallow-flights, per- 
haps only some ten days before, started on his north- 
ward voyage from Natal. 
It is one and the same migration of which we 
catch a glimpse when we see these visitors to our 
shores, whether it be summer or winter. All alike 
travel northward in spring and southward in autumn. 
But the British Isles form part of the northern region 
