204 
BIRDS OF PASSAGE. 
cies, quit the frosty regions of the north at the approach of 
cold weather, and spend the winter in the more tetnperate 
parts of Europe. . But the return of spring admonishes them 
when to leave these countries ; and they retire generally be- 
fore the end of April, to pass the breeding season on the con- 
fines of the arctic circle. The twite (Fringilla montium) 
breeds on the hills of Yorkshire and Westmoreland, but does 
not remain all the year in its summer habitation. For twites 
various bird.'. con g re g ate in multitudes about the beginning of October, and 
disappear ; but large flocks of them are seen at that time, or 
not long after, in the south of England. Thus are the two 
retreats of this migrating finch pretty well ascertained. But the 
same cannot be generally affirmed of those birds which retire 
from Britain in autumn. The swallow, however, is now 
known to winter in different parts of Africa ; and, in all pro- 
bability, future observers will discover the southern retreats of 
the other migrating species, partly on the same pontinent, and 
partly in the warmer countries of Europe, or in the correspond- 
ing districts of Asia. The last opinion must be received as a 
conjecture, but it has the recommendation of being probable j 
because those birds which return hither about the time of the 
vernal equinox, may be expected to pick up a livelihood near 
home during the preceding months, without accompanying the 
swallow to the mouth of the Senegal, in the 16th degree of 
north latitude. Finally, we may conclude, apparently with 
safety, that no bird retires in autumn farther from its summer 
residence than necessity requires, and that its winter abode is 
fixed by the article of food, which depends on the temperature ! 
of the place, and the appetite of the visitor. 
They return After making the foregoing imperfect remarks on the 
with summer, southern retreats of the migrating tribe, I come in course to the 
their*fbod.° r * cause which invites these wanderers northward, to spend the 
summer in higher latitudes. No sooner has the sun touched the ; 
tropic of Capricorn, than he begins to lessen his southern declina- 
tion, and to shine more directly upon the opposite hemisphere ; : 
every latitude of which experiences his animating influence in 
succession, commencing with the parts contiguous to the torrid 
zone, and proceeding gradually to the frozen regions within the 
arctic circle. The advances of spring towards the north, keep 
pace 
