410 The Bird 
Reserving the mention of partly ornamental tails until 
the last, we may now consider the use of this member as 
a prop or support to the bird as it clings to or makes its 
way up vertical surfaces. Four groups of birds which 
are thus distinguished are the woodhewers—a_ tropical 
Fic. 326.—Chimney Swift clinging to wall, resting upon tail. 
family,—the creepers, woodpeckers, and swifts. These 
birds really sit upon their tails, the feathers of which are 
adapted for this special use, while retaining perfectly the 
rudder function in flight. The tail-feathers of the Chim- 
ney Swift are peculiar in having the ends, for a short dis- 
