Organs of Nutrition 119 



Many birds carry in their beaks the grasses and 

 twigs with which they construct their nests, and if a sticky 

 fluid helped them to get their food, why would it not 

 also soften the twigs and make them easy to bend? Not 

 onh' this, but certain birds, such as our Chimney Swifts, 

 are provided with saliva in such quantities, and of such 

 tenacious consistency, that the entire nest — a mosaic of 



Fig. 91. — Nest of E.>5culent Swiftlet (edible bird's nest) composed entirely of saliva. 



small twigs, each about an inch in length — is set in saliva 

 cement, and fastened to the vertical side of a chimney 

 or charred tree-trunk by the same means. Even this is 

 only a step, or link, in the direction of the extreme use- 

 fulness of saliva, for the little East Indian birds known 

 as Swiftlets (one of which ornithologists call Collocalia 

 fuciphaga) make their nests entirely of saliva or mucus. 

 The second part of the scientific name, which means an 

 eater of seaweed, refers to the idea formerly held, that 



