T 



THE COMMON SWIFT. 



(Cypselus apus.) 



O ordinary observers a Swift appears so 

 much like a Swallow, that the only dif- 

 ference discernible by them is a difference of 

 colour. To the inquiring naturalist, however, a 

 much more important distinction presents itself 

 in the peculiar and remarkable anatomy of the 

 former bird. Not only has it a greater extent 

 of wing, moved by larger and more powerful 

 muscles, but the structure of the foot is curiously 

 adapted for climbing within the narrow crevices 

 which are usually selected as nesting-places. In 

 the Swallow and other Hirundines the toes are 

 long and slender three in front and one behind 

 in the same plane, as is usual with insessorial 



