THE TAIL—THE FEET 107 
With Woodpeckers, Creepers and Chimney Swift the tail is modified 
for use as a prop. 
The tail is exceedingly variable in form and is the seat of many 
interesting marks and colors which are displayed intentionally or when 
a. b 
Fia. 17. Tip of tail of (¢) Downy Woodpecker and of (b) Brown Creeper, to show the 
pointed shape in tails of climbing birds of different families. (Natural size.) 
the bird is in motion. Turkeys, Sage Cocks, Woodcock, spread the 
tail when strutting; with a host of birds white on the outer tail-feathers 
is conspicuously shown in flight or when the tail is nervously ‘jetted’ 
or twitched by the hopping bird (see Color). Some birds not closely 
related wag the tail (e.g. Spotted Sandpiper, Water-Thrush, Palm 
Warbler, Pipit), though why 
they should so do does not 
appear to be known. 
The Feet.—Birds’ feet serve 
a greater variety of uses than 
any of the four organs whose 
uses we are considering. Pri- 
marily they are of value as aids 
to locomotion, and the stu- 
dent should first note their 
length in wading birds like 
Flamingoes, Herons, and Stilts, 
and the relation between length 
of foot and length of neck. 
Aside from its length, the foot is. 
variously modified by the de- 
velopment of webs and lobes 
and lengthening of the toes and 
nails, for swimming, running, 
hopping, climbing and _ perch- 
ing. The growth in the fall of 
horn-like marginal fringes on 
the toes of the Ruffed Grouse 
and of feathers on the toes of 
Ptarmigan, presents an unusual 
case of seasonal adaptation 2 Fre. 18. Flamingo, showing relative length 
structure. of legs and neck in a wading bird. 
