THE LIVING WORLD. 
3ii 
Though there is considerable disparity in the size of the several species, 
this is about the only well-defined variation, for in habits they are all very 
similar. Being among the swiftest of birds we may expect to find them in 
nearly all parts of the world, coming and going with the season’s changes. 
In color they are uniformly sombre—black, brown or ashen-gray ; the bill is 
short but they have an enormous gape, which is kept spread when the birds, 
are on wing. The tail is square or forked, wings long and pointed, and legs - 
so short that movement on the ground is both slow and awkward. The 
goat-suckers have a wonderful provision of cilia, or hairs, radiating from 
the jaws, that spread out to act as a 
funnel, somewhat like the baleen in 
the Greenland whale, though in the 
latter the purpose is that of a strainer. 
They usually lay their eggs, two in 
number, in a rudely constructed nest 
either upon the ground or on a flat 
rock, and the eggs so nearly assimi¬ 
late in color to the surroundings that 
they are rarely found, the rudeness 
with which the nest is made aiding 
very much to prevent their discovery. 
Swallows, however, build their 
nests either in sandy banks, as 
our sand-swallows; or of clay ce¬ 
mented to a wall or rock, with a 
round hole for entrance, as our 
mud-marten; or of sticks glued together with the birds’ glutinous saliva, 
like our chimney-swallow ; or in the hollow of some decayed tree or box, like 
our house-marten. The sand-marten, or bank-swallow, is very abundant about 
the steep banks of American rivers, where 
it excavates a round hole several feet deep, 
in the rear end of which it builds a nest 
of down and lays four white eggs. The 
mud-marten, or barn-swallow, is about the 
same size as the sand-marten, but much more 
graceful in movement, as it is handsomer in 
color. The breast is white, back a glossy 
black, with a circlet of dull orange about 
the breast, and tail forked. It usually builds 
its nest of mud on the rafters of old barns, 
FALLOW swallow ( Glarealapratincola). rarely venturing into new buildings. The 
clay thus used is taken from the moist shore 
of some pond or stream, and first worked into a round ball before being con¬ 
veyed to the place of deposition. When the nest is completed the bird lines 
it with coarser feathers, over which it arranges a layer of down plucked from 
its own breast. Its eggs are also four in number, and of a pure white. The 
cliff-swallow constructs its nest very similar to that of the barn-swallow, except 
that the entrance is like the long neck of a bottle. Otherwise the habits of the 
two are identical. 
YOUNG OF THE AMERICAN NJGHT SWALLOW. 
