524 PASSERIFORMES CHAP. 
Africa, Borneo, and Burma. The summer migrants to Britain are 
Hirundo rustica, the Swallow, Chelidon urbica, the Martin, and 
Cotile riparia, the Sand-Martin. Swallows traverse Immense 
distances on their periodical journeys, while all perhaps shift their 
quarters to some extent for the winter. 
Hardly any sort of country comes amiss to these birds, 
though the neighbourhood of water is preferred, and for some 
species seems necessary. 
Spending their life chiefly 
in the air and alighting 
comparatively httle, they 
rapidly dart, twist, double, 
sail aloft, or skim- the 
water's surface in com- 
pany, at times chasing 
each other in sport or even 
fighting savagely. Insects, 
which form the whole of 
their sustenance, are ha- 
bitually taken on the wing, 
and the young are some- 
times fed, or building ma- 
terials snatched up, in full 
flight. A few species not 
uncommonly perch on 
trees, as Hirundo rustica, 
Fic. 115.—Swallow. Hirundo rustica. x4. 
Tachycineta albiventris, Petrochelidon nigricans, Psalidoprocne nitens 
and Procne tapera; the last-named, moreover, is exceptional in 
being non-gregarious, while it flits about with depressed wings 
and slow butterfly-like flight when not hawking. The majority 
are rarely seen on the ground, unless they are procuring mud for 
nidification ; but many roost on reeds or in their nests, and just 
before migration they settle in crowds on branches, fences, wires, 
and ridges of roofs. Hirundo, Chelidon, and Psalidoprocne bask in 
the sun on gravelly places. The twitter or warble of Swallows 
—uttered on the wing or at rest—and their squeaks of anger or 
alarm, are well-known ; the scream of Procne and the chirp of 
Stelgidopteryx being somewhat exceptional; when excited, however, 
the bill is not uncommonly snapped noisily. The nest may be 
cup-shaped as in our Swallow, Cottle rupestris, C. fuligula, and 
