108 Coues on the Eave, Cliff, or Crescent Swallow. 
It may be remembered in this connection that a happy conjunc- 
tion of circumstances is required to satisfy these birds. Not only 
are cliffs or their substitutes necessary, but these must be situated 
where clayey mud, possessing some degree of adhesiveness and plas- 
ticity, can be procured. The indication is met at large in the West, 
along unnumbered streams, where the birds most do congregate ; 
and their very general dispersion in the West, as compared with 
their rather sporadic distribution in the East, is thus readily 
explained. The great veins of the West, — the Missouri, the Co- 
lumbia, and the Colorado, — and most of their venous tributaries, 
returning the humors from the clouds to their home in the sea, are 
supplied in profusion with animated congregations of the Swallows, 
often vastly more extensive than those gatherings of the feathered 
Sons of Temperance beneath our eaves, where the sign of the order 
■ — a bottle, neck downward — is set for our edification. 
All are familiar, doubtless, with the architecture of these masons; 
if any be not, the books will remove their ignorance. But there 
are many interesting details, perhaps insufficiently elucidated in our 
standard treatises. It is generally understood that the most per- 
fect nest, that is, a nest fully finished and furnished with a neck, 
resembling a decanter tilted over, — that such a “ bottle-nosed ” 
or “ retort-shaped ” nest is the typical one, indicating the primitive 
fashion of building. But I am by no means satisfied of this. Re- 
membering that the Swallows are all natural hole-breeders, we may 
infer that their early order of architecture was a wall, rampart, or 
breastwork, which defended and, perhaps, enlarged a natural cavity 
on the face of a cliff. Traces of such work are still evident enough 
in those frequent instances in which they take a hole in a w r all, 
such as one left by a missing brick, and cover it in, either with a 
regular domed vestibule or a mere cup-like rim of mud. It was 
probably not until they had served a long apprenticeship that they 
acquired the sufficient skill to stick a nest against a perfectly smooth, 
vertical support. Some kind of domed nest was still requisite, to 
carry out the idea of hole-breeding, a trait so thoroughly ingrained 
in Hirundine nature, and implying perfect covering for the eggs ; 
and the indication is fully met in one of the very commonest forms 
of nest, namely, a hemispherical affair, quite a “ breastwork ” in 
fact, with a hole at the most protuberant part, or just below it. 
The running on of a neck to the nest, as seen in those nests w r e con- 
sider the most elaborate, seems to merely represent a surplusage of 
