SOLITARY AND GREGARIOUS. 133 



social habits of birds, it would seem that their so- 

 ciality 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 (Loxia soda) 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 Egyptraising 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 

 M 



