SOLITARY AND GREGARIOUS. 133 
social habits of birds, it would seem that their so- 
ciaiity produces no apparent result, except it may 
be the appointment of a sentinel to give intimation 
of danger, if indeed such appointment (as may well 
be doubted) actually takes place. Except in the 
instance of the sociable grosbeak (Lozia socia) of 
Africa, we do not recollect any authentic instance 
of birds uniting their efforts to assist in performing 
a common work. Even in this instance, the accu- 
rate observations of M. Vaillant have proved, that 
so far from building streets, as Paterson and others 
represent these birds to do, they merely build their 
nests in actual contact, as rooks may sometimes be 
observed to do in this country. The notion of 
their building streets is of the same character with 
Pliny’s account of the swallows in Egypt raising an 
embankment to oppose the inundation of the Nile, 
adopted by him from some hasty observer who 
had seen the bank-swallows (Hirundo riparia), not 
building (as he supposed), but mining into an es- 
carpment of the river. In the same way we find 
it related by authors of celebrity, that when a pair 
of sparrows take felonious possession of the nest 
of a swallow, the swallow summons its compan- 
ions to its assistance, when they all unite in a body 
to bring a sufficient quantity of mortar to entomb 
the robber-sparrows alive in the nest. This story 
‘is obviously imaginary, and the fiction is shown 
from the impossibility of so entombing, by means 
of clay, a bird with so powerful a bill as the sparrow. 
M. Dupont de Nemours gives the following singu- 
lar account of what fell under his own observation: 
“I remarked,” he says, ‘a ‘swallow which had un- 
happily, and I cannot imagine in what manner, 
slipped its foot into a slipknot of packthread, the 
other end of which was attached to a spout of the 
College of the Four Nations. Its strength was ex- 
hausted; it hung at the end of the thread, uttered 
cries, and sometimes raised itself as if making an 
