spection reveals the fact that his head and neck picture several reed stems, 

 with their shadows, and that the peculiar attitude is necessary for the most 

 effective display of this obliterative or at most semi-mimetic pattern. (Semi- 

 mimetic, inasmuch as the several reeds seem to occupy about the space really 

 filled by the bittern's neck, although the effect is still of the neck's dissolution 

 into its general background and surroundings.) But in all or most such cases, 

 in spite of the evident paramount importance of the obliterative function, it is 

 undeniable that the mimetic effect is sometimes achieved, to a greater or less 

 extent, and hence that it must be a factor in the development of the peculiar 

 actions and even the particular coloration of certain birds. Just how large 

 or how small a factor, who shall say ( ?) ; but recognizing the dominant impor- 

 tance of the obliterative laws even in these few special cases, one cannot sup- 

 pose that the other principle has more than a very limited and slender scope. 

 Nevertheless, it is not to be ignored. A Ruffed Grouse picking buds high 

 up among the leafless twigs of winter trees, must often be seen in a light and 

 against a background (as of blank snow) which does not favor its obliterative 

 coloration. Then the extraordinarily slender, stick-like form (accentuated by 

 peculiar angles in the head and neck, and by the erected occipital crest) which 

 the bird assumes the moment it is alarmed, does certainly render it good ser- 

 vice in the direction of protective 'mimicry.' At such times the bird's ene- 

 mies must often mistake him for a knotted branch. Yet, on the other hand, 

 even at such times, thanks to the bird's perfect obliterative shading and pat- 

 tern, the chance is great that he will not be seen at all (as a solid object), and 

 this chance is probably still of paramount importance. 



But there is one bird at least in whose case the balance of importance may 

 tip toward the mimetic function of specialized perching-habits. This is the 

 big woodland goatsucker of northern South America, etc., the "Poor-me- 

 one" of Trinidad negroes (Nyctibius jamaicensis), whose characteristic 

 perching place, both by day and night, is the top of a broken stump or up- 

 right branch. Here it sits almost erect, and motionless, with its long and 

 ample tail pressed flat against the side of its perch, which seems to be con- 



lOI 



