[Illustration]
In caves near the ocean in the Far East nest myriads of tiny swiftlets
whose chief impact on the civilized world is that their nests provide
an edible article of commerce. "Birds' nest soup" at once comes to the
mind of the Occidental, few of whom have ever eaten of the nests, or
even seen the birds to know them. For those who would like to see the
nests, some museums have them on exhibition, such as in the Chicago
Natural History Museum, where two nests are placed in their natural
setting, and beside them is a quantity of the material of commerce in
its raw state.
The birds themselves are dusky-colored swifts only a few inches
long, and belong to a group of swifts that represents perhaps the
most puzzling problems of species identification in the bird world.
As yet we do not know even how many species there are. The genus is
called _Collocalia_. Only some of its members make the edible nests;
others mix so much moss into the nest that it is useless for soup. One
species has the scientific name of _esculenta_, given in reference to
the supposed edible nature of the nest, but through error the name was
applied to a species whose nests are not edible. In habits all these
swiftlets seem very similar, flying about with a rather weak flight for
a swift, catching their insect food on the wing.
A number of swifts, including our chimney swift, use the secretion of
their salivary glands as a glue to stick together their nest, and to
stick it to the wall of a cave, the inside of a hollow tree, or the
inside of a chimney. But some of the edible-nest swifts go further
and make their nest entirely of this secretion from their enormously
enlarged salivary glands. This material, as it comes from the mouth
of the bird, resembles a saturated solution of gum arabic and is very
viscid. If one draws out a strand from the mouth of the bird and sticks
it on a rod, by rotating the rod and winding up on it the thread of
saliva one can empty the salivary glands of the bird. This material
dries quickly, and is the material of which the nest is made. When
the bird makes its nest, which it does in large colonies in caves,
it flies up to the rock wall, applies the saliva to the rock in a
semicircle or horseshoe. Gradually a little shelf is built out, and in
the finished nest one can see the many little strands that have gone
into the structure. It may take the birds as long as three months to
make this nest, even if undisturbed. The birds lay their two eggs in
the nest, and raise their naked, helpless hatchlings into facsimiles of
themselves in it.
But in the Orient, especially in China, the nests are highly prized by
epicures as a delicacy. As the supply is limited the price is high. A
note with some material we saw stated that the price was $12 to $36 a
pound in Siam.
The climbing for and collecting of these nests requires daring, skill
and is not without danger. The nests may be far back and high up in
the cave. Ropes and poles may have to be fixed in place to aid the
climber, who has a flaming torch in one hand and carries a sack or
basket for the nests. In Siam, at least, the collecting of these nests
was hereditary, father training son. The rights to collect nests are
valuable. In Siam, where the rights to collecting the nests were vested
in the state, revenue of as high as £20,000 has been received from the
rights for this collection.
The nests are said to be of highly nitrogenous material, and contain
about 50 per cent of protein and 7½ per cent of mineral matter. Their
use as food is an Oriental custom, but an Occidental opinion of their
flavor is that it is bland, and an appreciation of it needs to be
cultivated. The price of these nests is so great that unscrupulous
persons have manufactured spurious nests. These nests are made from
agar-agar, the jelly made by boiling down certain seaweed, and are so
cleverly flavored that only connoisseurs can detect the fraud.
We usually think of these nests in connection with birds'-nest soup,
which may be made with chicken or beef broth and then the cleaned
material of the nest added like tapioca or vermicelli. Sometimes a
sweet soup is made. Sometimes lotus seeds, sugar, and the nest material
are used in the preparation of the dish. But in the Orient, at least
formerly, they're considered to have medicinal qualities, too. It is
said that when combined with ginseng they are capable of restoring life
to a person on the point of death. In Northern China where the winter
is bitterly cold, it is a general belief that the blood congeals and
can only be thawed out by drinking a soup made of these nests. The
list of further benefits, such as against tuberculosis, as a tonic,
stimulant, and a pacifier of the stomach, recall advertisements of
patent medicines.