_FISSIROSTRES. — HIRUNDINID &. 151 
for their feet are always very short, weak, and generally 
so imperfect as to be of no farther use than to rest 
the body after flight: their food is exclusively insects, 
captured upon the wing. To accomplish this, nature 
has given to their mouth an enormous width, by which, 
superadded to their amazing flight, and rapidity of 
movement, they are almost sure to capture <heir prey. 
Who, that has watched the swallow or the goatsucker, 
has failed to recognise these peculiar perfections? As 
the nocturnal goatsuckers frequently prey upon beetles 
and large moths, the mouth, in such species, is defended 
by stiff bristles: but these appendages are rendered 
unnecessary to the swallows; their game consisting 
entirely of those little soft insects seen in the air on a 
summer’s evening, or sporting on the flowers of a 
sunny field. The goatsuckers choose the twilight, and 
catch their food precisely in the same way, excepting, 
indeed, that their little short feet are sometimes used 
for the same purpose, — a most singular part of their 
economy, first noticed by our countryman, White. 
Some of these nocturnal birds (Pogardus Cuv.) have 
a bill nearly as strong as an owl; others are furnished 
with forked tails of excessive length ; and one species, 
discovered during our researches in Brazil (Caprimulgus 
diurnus Tem.), quits the nocturnal habits of its 
congeners, and in cloudy days may be seen in troops 
of fifteen or twenty, skimming over the surface of 
ponds, precisely in the manner of swallows: these two 
groups, in fact, are connected by certain swifts; for the 
Balassian swift * is described as “‘a nocturnal bird, 
appearing at sunset, and going to rest at sunrise.” 
 (171.) We thus enter the family of swallows 
(Hirundinide), which present many singular variations 
of structure among themselves: in the true swifts 
(Cypselus), the hind toe is so placed that it can be 
brought nearly forward, and all four are armed with 
very strong crooked claws, giving to the bird such a 
firm grasp, that it can sustain itself by the side of 
* Gen. Hist, of Birds, vii. p, 329. 
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