. Bird-lore . Robins and Sparrows or birds with whitefeathers in unusual places are not at all infrequent. Usually this partialalbinism is symmetrical on each side of the bird but it is not always so. Theexact cause of albinism is not known though it is thought to be a form ofphysical weakness due to inbreeding or to some other cause. More unusual than albinism is what is called dichroniatism (from the Greekdi+khromatikos, meaning two-colored) or the occurrence in a species of twocolor phases irrespective of age, sex, or season. The familiar Screech Owlaffords us a good example where extremes
. Bird-lore . Robins and Sparrows or birds with whitefeathers in unusual places are not at all infrequent. Usually this partialalbinism is symmetrical on each side of the bird but it is not always so. Theexact cause of albinism is not known though it is thought to be a form ofphysical weakness due to inbreeding or to some other cause. More unusual than albinism is what is called dichroniatism (from the Greekdi+khromatikos, meaning two-colored) or the occurrence in a species of twocolor phases irrespective of age, sex, or season. The familiar Screech Owlaffords us a good example where extremes of red and gray individuals occur aswell as intermediates. These may be, and often are, individuals from the samenest, and they may be all males or all females. It is apparently due to anexcess of red or brown pigment and may represent but a step toward likewise occurs with certain other owls, and with certain Hawks,as well as with some species of Herons. The case of the rare Corys Least. A DlSAliLEl) CORYS LIOAST s|)ecics is proljiibly only a color-phase of the common Least liitteni, but such ;in,it is called, is rare except with certain Herons, Hawks, and Owls The Audubon Societies 263 Bittern is one of the mostinteresting as scientists arenot yet agreed as to whetlierit represents a distinct spec-ies on tlie verge of extinctionor whether it is but a darkphase of the common LeasBittern. Its color pattern isapparently identical with thatof the common Least Bitternbut all of the buffs have beenreplaced by chestnut. But to return to the gor-geous Tanagers and the incon-spicuous Grouse, surely thereis some reason for the differ-ence in coloration whichstudy might lead us to under-stand. In thinking over thebirds with which we are familiar we soon discover that brilliant colors, in al-most every species, are restricted wholly to the males, and a moments reflec-tion suggests to us that the law of The Survival of the Fittest would
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