EVOLUTION OF THE COLORS OF BIRDS. 197 



I am not sure that anj'^ instance exists among North 

 American land birds of (6) special protective resem- 

 blance. The nearest approach to it is the perfect imi- 

 tation of the bark of the tree by the markings of the 

 back of the brown creeper {Certhia familiaris americana). 

 This is in reality only an unusually complete case of gen- 

 eral protective resemblance. Mr. Wm. V. Praeger has 

 suggested an instance among wading birds which should 

 be inserted here as illustrating this very unusual class. 

 He says:* "To the protective colors which are unusual 

 among the shore birds I had always considered the 

 neck and head marking of the genus JSgialitis a strik- 

 ing and curious exception, till a short time ago, when 

 looking at an JS. semijoalmata, which I had wounded, 

 trying to hide by crouching in a hollow in the sand; and 

 while admiring the perfect blending of its brown shades 

 with the surroundings, I saw in its white rings one of 

 the commonest objects of the sea shore — the empty half 

 of a bivalve shell. The white about the base of the bill 

 was the " hinge," the collar the outer rim, and the top 

 of the head the cavity of the shell, filled — as they 

 usually are — with sand. In the cabinet drawer the re- 

 sembance is not so noticeable, but such resemblances 

 rarely are, and it was striking among the natural sur- 

 roundings when I first observed it, and it is most perfect 

 when the bird is crouching as it does in the presence of 

 danger or when on its eggs." 



(2) Anticryptic colors differ from the preceding 

 merely in the fact that they are used by rapacious birds 

 in approaching their prey, instead of by harmless 

 species in avoiding danger, (c) General aggressive col- 

 ors are illustrated by the mottled plumage of most of the 

 owls, the burrowing owl (Speoiyto cihuiculavio hypugcea), 

 being a particularly good example. These forms are all 



*Auk, viii, p. 236. 



