Order 2. PASSERINE. 183 



chiefly in the air, [even copulating on the wing], and pursue insects in flocks, aonietimes 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 diflTerent type of form froin any of the foregoing. The 

 entire anatomy, if we except the trachea and toes, and the latter more than any other genus, vei 

 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 

 stemo-tracheales ; there are immense salivary glands, as in the Humming-birds, which secrete a viscid 

 mucus, and no intestinal cceca ; 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, Tem.) — Black, with a white throat, [and common 

 tliroug;hout Europe in summer, making but a short stay. The young- do not moult before the second autumn.] 



The White-bellied Swift (//. melba, 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.-etura, Swainson. 

 Tliere 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 laii-feathers, &c. Their rapid flight depends entirely on 

 external modifications, for which reason it is much less capalde of protraction than in the Swifts, as is 

 particularly shown by their weariness after performing migration, on wliich 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. urbica, 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 wuulo\v-e.aves, 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 

 rufous, 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. riiftila, Tem., or H. daurica, Sav., and H. rtipestris, Lin.] 



Among the [very immerous] species foreign to Europe, may be noticed a very small one from the Indian Archi- 

 pelago, the //. esculenta, Lin., which is brown above, whitish below and at the tip of its forked tail. It is ccle 

 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 thero an important article of traffic 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 Moph-hunters {Caprimulgtis, Lin.) — 

 Have the same light, soft plumage, minutely mottled with grey and brown, that characterizes other 

 night-birds. Their eyes are large ; the beak, still more deeply cleft than in the Swallows, and 

 [generally] armed with strong vibrissse, is capable of engulphing the largest insects, which are retained 

 by means of a glutinous saliva, [as in the Swifts] ; 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 



