MIGRATION. 
895 
Gull, Caspian Tern, Common Tern, and Little Tern. 
This list does not include those species which descend 
from the mountain districts of India to the lowlands, as 
they may probably be coupled with the birds of passage. 
How many of these last pass from over India and the 
Malay peninsula towards the Sunda and the other islands 
of Australasia, we do not at present know : that some do, 
however, we are convinced. 
The birds of North America migrate as regularly, and 
in equally as great numbers, as those which inhabit the 
northern portion of the Old World. The season of 
migration is much about the same as with us; but a 
certain portion only of the mass of birds of passage travel 
in a north-easterly and south-westerly direction. Unless 
compelled by necessity, no land-bird, nor for that matter 
aquatic-bird either, ever passes the broad ocean; they 
all, on the contrary, keep to the land as long as possible. 
The principal retreat of the North-American migratory 
birds is to the country bordering the Gulf of Mexico, and 
especially Mexico itself, which, lying as it does within 
three different zones, possesses great variety of climate. 
Some of these birds, however, go as far as Central 
America and the West Indies, and even Venezuela and 
New Granada. These last—as well as those which have 
taken up their quarters in Mexico, Texas, Louisiana, 
Mississippi, Alabama, Georgia, and Florida—all take a 
more or less north-westerly and south-easterly direction. 
Whoever is acquainted with the American representa¬ 
tives of those families whose Old-World members have 
been designated birds of passage, will not require a list 
of the North-American migrants. One will rarely err 
in assuming that all the birds of the Western Hemi¬ 
sphere whose habits resemble those of the birds of 
