SWIFT 936 
it generally disappears from England very early in August, though 
occasionally to be seen for even two months later. 
The Swift commonly chooses its nesting-place in holes under the 
eaves of buildings, but a crevice in the face of a quarry, or even a 
hollow tree, will serve it with the accommodation it requires. This 
indeed is not much, since every natural function, except sleep, 
oviposition and incubation, is performed on the wing, and the 
easy evolutions of this bird in the air, where it remains for hours 
together, are the admiration of all who witness them. Though 
considerably larger than a Swallow, it can be recognized at a 
distance less by its size than by its peculiar shape. The head 
scarcely projects from the anterior outline of the pointed wings, 
which form an almost continuons curve, at right angles to which 
extend the body and tail, resembling the handle of the crescentic 
cutting-knife used in several trades, while the wings represent the 
blade. The mode of flight of the two birds is also unlike, that of 
the Swift being much more steady, and, rapid as it is, ordinarily 
free from jerks. The whole plumage, except a greyish-white patch 
under the chin, is a sooty-black, but glossy above. Though its 
actual breeding-places are by no means numerous, its extraordinary 
speed and discursive habits make the Swift widely distributed ; 
and throughout England scarcely a summer’s day passes without 
its being seen in most places. A larger species, C. melba or alpinus, 
with the lower parts dusky white, which has its home in many of 
the mountainous parts of central and southern Europe, has several 
times been observed in Britain, and two examples of a species of a 
very distinct genus, Acanthyllis or Chetura, which has its home in 
northern Asia, but regularly emigrates thence to Australia, have 
been obtained in England (Proc. Zool. Soc. 1880, p. 1). 
Among other peculiarities the Swifts, as long ago described 
(probably from John Hunter’s notes) by Home (Pil. Trans. 1817, 
pp. 332 et seqq., pl. xvi.), are remarkable for the development of 
their salivary glands, the secretions of which serve in most species 
to glue together the materials of which the nests are composed, 
and in the species of the genus Collocalia form almost the whole 
substance of the structure. These are the “edible” nests so 
eagerly sought by Chinese epicures as an ingredient for soup, and 
their composition, though announced many years since by Home 
(ut swprd), whose statement was confirmed by Bernstein (Act. Soc. 
Sc. Indo-Neéerl. iii. Art. 5, and Journ. fiir Orn. 1859, pp. 111-119), 
has of late been needlessly doubted in favour of the popular belief 
that they were made of some kind of sea-weed, Algx, or other 
vegetable matter collected by the birds.! It may be hoped that the 
examination and analysis made by Dr. J. R. Green (Journ. of Physiol. 
vi. pp. 40-45) have settled that question for all time. These re- 
1 Hence one species has been called Collocalia fuciphaga. 
