156 NATURAL HISTORY. 
wheeling with wonderful velocity, occasionally soaring 
very high, and uttering its shrill screams. It captures 
great quantities of insects to give to its young, retaining 
them in a kind of pouch under the tongue. Our Chim- 
ney Swallow is one of the Swifts. It is a social bird, ap- 
pearing in flocks, and making its nest in tall hollow 
trees or in unused chimneys. It is amusing to see them 
go into achimney. The flock wheels round and round, 
and as they come down near the chimney those that are 
lowest drop in at each turn till the whole have descend- 
ed. The Bank Swallow, or Sand Martin, which we see 
so often making holes in sand-banks with its awl-shaped 
bill, has its counterpart in Europe. The Martins, which 
so familiarly inhabit the boxes set up for them by man, 
are Swallows. Appearing in the extreme south of the 
United States the first part of February, they arrive in 
New England the latter part of April, and in May they 
are seen as far north as Hudson’s Bay. They begin to 
emigrate from thence southward in August.* 
257. The Todies are birds of gaudy plumage and rapid 
flight, restricted almost entirely to tropical regions. 
* There is one species of Swallow which furnishes a singular arti- 
cle of diet, highly prized by the Chinese. This article is the nest of 
the bird. The chief material of which the nest is composed has been 
a subject of much dispute, some supposing it to be a kind of sea-weed, 
and others a substance derived from the spawn of fishes. ‘‘It is now 
ascertained,” says Carpenter, ‘‘ that this substance is secreted by enor- 
mously developed salivary glands; a few fragments of grass, hair, and 
other substances are generally mixed with it. The purest nests con- 
sist almost entirely of gelatinous matter, which, dissolving readily in 
water, is employed in making rich soups and gravies. The collecting 
of these nests is a proceeding of great danger; but a large number of 
persons are employed in it, as may be judged from the quantity sent 
to China. About 27,000 lbs. are annually transmitted from Java, 
and these are of the best quality. A still greater quantity is obtained 
from the Suluk Archipelago, and much, also, from Ceylon and New 
Guinea. It is calculated that about 30,000 tons of Chinese shipping 
are engaged in the traffic, and that the value of their freights is above 
£280,000.” 
