other hand, the cases are many of the occasional mimetic aspect of birds 

 whose main protective equipment is purely obliterative, like the ruffed grouse, 

 screech owl, etc., just referred to, and the terrestrial goatsuckers mentioned 

 in an earlier chapter. Other slight and dubious encroachments of mimicry 

 into the domain of obliterative coloration have been mentioned here and 

 there in the foregoing pages, as for instance in connection with the flowerlike 

 bills and frontal appendages of certain water birds (Chapter XV). 



The gorgeous "beauty spots" of hummingbirds, most commonly occurring 

 on the head and throat, are certainly not mimetic, though they have some- 

 times been considered so. Flowerlike though many of these brilliant head- 

 dresses are, there is not, I believe, one among them all which really imitates 

 a single flower, in minute and near detail. On the contrary, they are all 

 flashing pictures of flowery and leafy landscape, at uncertain distances. Hum- 

 mingbirds' metallic colors mark the very climax of the development of iri- 

 descence, the high obliterative power of which principle has already been ex- 

 plained. Their changeableness often ranges from duU, velvety soot-color to 

 the intensest gleaming of pure red, blue, green, orange or purple, as the case 

 may be; and sometimes several of these bright colors coexist in the same 

 feathers, showing either separately, in different lights, or intermixed, in one 

 light. But the change from one bright color to another is less characteristic 

 of himimingbirds' iridescence than the change from dull black to keenest 

 brightness. It is in the fullness of this change, and the extreme brilliancy 

 of the high-light tints, that the supremacy of their coloration lies. Perhaps, 

 after all, they do not quite deserve the palm for iridescence, in the strict sense 

 of the word, but for changeable and luminously brilliant color, they are almost 

 unique among animals. Indeed, they have an almost unrivaled obliterative 

 equipment. Behind the dazzling, scintillating blaze of its jeweled head, how 

 can the little round body of a hummingbird be seen ? That shifty blaze of 

 red or green or purple light, one instant partly clouded over, and in the next 

 flashing out into the sharpest sunlike sparkles, completely eclipses and masks 

 the form and. solidity of the body, now veiling it, and now piercing it, so to 



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