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.