with the birds' half-terrestrial habits, have yet much in common with ducks' 

 grizzled water-patterns; and the two types are connectal by intermediate 

 forms, e. g., the breast-pattern of the Ruddy Duck {Erismatura jamaicensis). 



Ducks have still another very characteristic obliterative marking, the 

 bright-colored "speculum" — & broad band, often of metallic green, blue, and 

 purple, crossing the middles of the secondary wing feathers. This marking 

 can but poorly serve the purpose (commonly supposed to be the main function 

 of all such marks) of display 4n flight, for the color is confined to the tops 

 of the outer webs of the wing feathers, and so only makes a continuous band 

 when the wing is folded. Its obliterative use, on the other hand, is most 

 pronounced. It gives the effect of a 'window' through the body of the bird 

 to the water or vegetation beyond.^f This speculum is almost always of some 

 characteristic water tint — ^blue, green, or gray. Often it is highly iridescent, 

 which makes it additionally effective (as will be explained at length in a later 

 chapter). On some species, such as the Scaups (Aythya marila, etc.), it is 

 white. But even pure white serves the same 'obliterative' purpose, picturing 

 a sky-reflection on the background-water. 



All these factors in the disguising costumes of ducks are usually parts of 

 an 'obliterative' scheme based on full obliterative shading. Very few ducks 

 lack this counter shading, and most of them have it in full development, 

 particularly the females, and the males in post-nuptial summer plumage. 

 The singular change to a dull-colored summer dress, like that of the females, 

 which most male ducks yearly undergo, is coincident with their loss, and lack, 

 for many weeks, of all flight-feathers. Discussing this phenomenon, an 

 eminent English ornithologist remarks: J "Most of these birds {Anatidce) 



* Much the same purpose is served by the beautiful metallic spots or patches of water-color 

 (deep blue, green, and violet) on other parts of the body, worn by many sea ducks, notably Steller's 

 Eider. This bird has indeed a supremely beautiful pattern of ice and water pictures. 



t Little used while the duck is swimming, but greatly when he walks about on the adjacent shore, 

 in far greater danger from his enemies. These speculums prove, also, to have a wonderful power to 

 obliterate their wearers against the sky, to the eyes of creeping enemies that flush them. — A. H. T. 



X See the "Encyclopedia Britannica," vol. iii, p. 776 (of the R. S. Peale Reprint). 



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