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Bird - Lore 



snow-white, having no pigment whatsoever, the eyes being red owing to the 

 blood showing through the iris. They are apparently much more frequent 

 with domestic animals than in the wild state, as in the familiar white mice, 

 rats, and rabbits, but they are likely to occur at any time with any species. 

 The brown pigment seems the most likely to disappear, pure albinos of birds 

 having red or yellow in their plumage being extremely rare. The Meadowlark 

 in the accompanying photograph, for example, shows a well-defined tinge of 

 yellow on the underparts and before the eye. Partial albinos are much more 

 frequent with all species, and mottled Robins and Sparrows or birds with white 

 feathers in unusual places are not at all infrequent. Usually this partial 

 albinism is symmetrical on each side of the bird but it is not always so. The 

 exact cause of albinism is not known though it is thought to be a form of 

 physical weakness due to inbreeding or to some other cause. 



More unusual than albinism is what is called dichromatism (from the Greek 

 di+khromatikos, meaning two-colored) or the occurrence in a species of two 

 color phases irrespective of age, sex, or season. The familiar Screech Owl 

 affords us a good example where extremes of red and gray individuals occur as 

 well as intermediates. These may be, and often are, individuals from the same 

 nest, and they may be all males or all females. It is apparently due to an 

 excess of red or brown pigment and may represent but a step toward melanism. 

 Dichromatism likewise occurs with certain other owls, and with certain Hawks, 

 as well as with some species of Herons. The case of the rare Cory's Least 



A DISABLED CORY'S LEAST BITTERN 



This species is probably only a color-phase of the common Least Bittern, but such 'dichromatism', as 



it is called, is rare except with certain Herons, Hawks, and Owls 



