56 Trans. Acad. Sci. of St. Louis 



While the high keel of the Swift's breastbone, able to 

 support large pectoral muscles, corresponds to the untir- 

 ing power of flight, the long tibiae, short tarsi and strong 

 claws are most ably adapted to the purpose of which they 

 are intended, that of clinging in upright position to per- 

 pendicular surfaces, in which the stiff, bristly tail feath- 

 ers serve as a brace. It is in these places that the Swift 

 not only finds rest and spends its nights, but also builds 

 its nest, a semi-circular, half-saucer-shaped basket, a 

 curious and unique structure of short bits of twigs glued 

 together by the saliva of the bird. Male and female are 

 both provided with glands situated below the tongue pro- 

 ducing this glutinous substance, but only during the time 

 of nest building and in small daily quantities. It is a 

 colorless liquid, which soon hardens to a yellowish var- 

 nish, a strong cement in a dry place, but soluble in water. 

 As this glue is the only means by which the nest is fas- 

 tened to the wall, long spells of rain loosen its hold, caus- 

 ing the destruction of its contents. If this happens early 

 in the season, a second attempt is made, and this explains 

 why late broods are found, giving rise to the mistaken 

 belief that two successful broods are reared. By actual 

 observation it has been established that to raise a brood 

 of Swifts takes much longer than formerly supposed. It 

 takes the Swift longer to build a nest than other birds, 

 because the glue put down one day has to harden before a 

 new layer can be added. While it dries in one day of warm, 

 dry weather, it takes longer in wet and cool weather. 

 Starting the construction of a nest a good layer of glue 

 is smeared against the wall and a few short bits of twigs 

 are stuck to it while yet wet. These twigs are broken 

 from dry branches of trees by the bird flying repeatedly 

 against them and taken hold of and carried to the nest 

 with their feet. The whole process of nest building, egg 

 laying and raising of young to the state when they can 

 feed themselves is a slow one and requires fully two 



