16 EVOLUTION OF BIRDS. 



ers, Woodhewers, and Swifts, even some Finches and 

 the Bobolink, that use their tail to support them when 

 perched on swaying reeds, have the feathers more or 

 less pointed and stiffened. Furthermore, this is just the 

 result we should expect from a habit of this kind. But 



b 



FIG. 3. Tip of tail of (a) Downy Woodpecker and of (b) Brown Creeper, to 

 show the pointed shape in tails of creeping birds of different families. 

 (Natural size.) 



I do not understand how the Woodpecker's spear-tipped 

 tongue could have resulted from the habit of impaling 

 grubs, and in this case I should be inclined to regard 

 structure as due to a natural selection which has pre- 

 served favorable variations in the form of this organ. 



I have not space to discuss this subject more fully, 

 but trust that enough has been said to so convince you 

 of the significance of habit, that when you see a bird in 

 the bush it will not seem a mere automaton, but in each 

 movement will give you evidence of a nice adjustment 

 to its surroundings. Eemember, too, that evolution is a 

 thing of the present as well as of the past. We may not 

 be able to read the earlier pages in the history of a species, 

 but the record of to-day is open to us if we can learn to 

 interpret it. 



This may be made clearer, and the importance of a 

 study of habit be emphasized, if I briefly outline the rela- 

 tion between the wings, tail, feet, and bill of birds and 

 the manner in which they are used. We are in the field, 

 not in the dissecting room ; our instrument is a field glass, 

 not a scalpel, and in learning the functions of these four 



