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PASSERINiE. 195 
chiefly in the air, [even copulating on the wing], and pursue insects in flocks, sometimes at a great { 
altitude, uttering discordant screams. Thev nestle in the holes of walls and rocks, and climb perpen- | 
dicular surfaces with facility. 
[With this genus, we enter upon a very different type of form from any of the foregoing. The 
entire anatomy, if we except the trachea and toes, and the latter more than any other genus, very 
closely resembles that of the Humming-birds. It is only in superficial or adaptive modifications that 
they accord with the Swallows. The lower larynx is furnished with only one pair of muscles, the ordinary 
sterno-tracheales ; there are immense salivary glands, as in the Humming-birds, which secrete a viscid 
mucus, and no intestinal coeca ; the clothing feathers have a considerable supplementary plume. 
It is necessary to subdivide them into 
The True Swifts {Cypselus, as restricted) — 
Which have a forked tail, and feet as already described. 
Of several species, two only inhabit Europe.] 
The Common Swift {Hirundo apus, Lin. ; C. murarius, Tern.)— Black, with a white throat, [and common 
throughout Europe in summer, making but a short stay. The young do not moult before the second autumn.] 
The White-bellied Swift (//. nielba, Lin). — Larger, and brown, with white collar and medial inferior region. [Of 
rare occurrence in Britain. Unlike the Swallows, these birds rear but one brood in a season. There are several 
more.] 
Others have stiff, pointed tail-feathers, as in the Woodpeckers, and the thumb directed backward ; 
but they pass insensibly into the preceding. They constitute the 
Ch.f.tura, Swainson. 
There is one common in North America, the Chimney Swallow of Wilson ; also others in the eastern hemisphere, 
one or more of which inhabit Australia. 
The True Swallows {Hirundo, Cuv.) — 
Have the feet and sternum similar to those of ordinary Passerince ; [also the complex inferior larynx 
as usual, small coeca to the intestine, twelve tail-feathers, &c. Their rapid flight depends entirely on 
external modifications, for which reason it is much less capable of protraction than in the Swifts, as is 
particularly shown by their weariness after performing migration, on which occasions they have been 
seen to alight flat upon the sea.] 
Some have the feet feathered to the claws, have a slight tendency to revert the posterior toe, and a moderately 
forked tail ; as 
The Martin Swallow (H. urhica, Lin.).— Glossy black above, white below and on the rump. Every one is 
acquainted with the solid mud-built nest of this species, fixed under window-eaves, the jutting roofs of houses, &c. 
Others have naked feet, and a more sharply forked tail, the exterior feathers of which are often much 
prolonged. As 
The Chimney Swallow {H. rustica, Lin.).— Above [and across the breast] glossy black, the forehead and throat 
nifous, beneath [and a spot on each except the middle tail-feathers], white : it builds generally in chimneys. 
The Bank Swallow {H. riparia, Lin.). — Brown above and across the breast, the throat and under-parts white. 
[A small tuft of down on each foot.] It burrows and forms its nest in steep banks. [There are two others in 
southern Europe, H. rufida, Tern., or H. daurica, Sav., and H. rupestris, Lin.] 
Among the [very numerous] species foreign to Europe, may be noticed a very small one from the Indian Archi- 
pelago, the H. esculenta, Lin., which is brown above, whitish below and at the tip of its forked tail. It is cele- 
brated for its nest, formed of a whitish gelatinous substance arranged in layers, and obtained by macerating [in 
the stomach] a peculiar species of fucus. The nutritious qualities attributed to these nests in China have ren- 
dered them an important article of traflfic in that country. 
[It is interesting to note that the Purple Swallow {H. purpurea) of America, which has a stouter beak than the 
others, feeds much on berries, at least while in its winter quarters, as observed by M. Audubon. The relation of 
this genus to the Phibalures has been already remarked]. 
The Moth-hunters {Caprimulgus, Lin.) — 
Have the same light, soft plumage, minutely mottled with grey and hrown, that characterizes other 
night-birds. Their eyes are large ; the beak, still more deeply cleft than in the Swallows, and 
[generally] armed with strong vibrissas, is capable of engulphing the largest insects, which are retained 
by means of a glutinous saliva, [as in the SAvifts] ; the nostrils, placed at its base, are like small 
tubes ; their wings are lengthened ; the feet short, with plumed tarsi, and a membrane connecting the 
basal portion of the toes ; the thumb itself is thus connected with the internal toe, and is directed 
o 2 
