230 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



"la a state of domesticatiou, as we are well aware, we constantly 

 notice a great variety in the colors of birds of the same kind. In the 

 same brood of chickens we see black and white, speckled and plain, all 

 evidently the progeny of the same stock. Similar variations are notice- 

 able in the domestic duck, which is the progeny, by long descent, from 

 the wild mallard, which never varies when in its undomesticated life. 

 Yet no rule has been supposed to be more unvarying than that all wild 

 birds present certain uniformities of size, shape, bill, leg, colors and the 

 like, by which science establishes orders, genera and species. Each 

 I)articular species of birds, and there are some twelve thousand or more, 

 now recognized in the world, has been supposed to present the same 

 uniform appearance as to size, shape and marking. There are, of course, 

 great variations caused by age, sex and season. The same ptarmigan 

 is red in summer and pure white in winter. The same species of heron 

 is white in youth and bright cerulean blue in maturity; the same water- 

 rail is jet-black in early life and of brighter colors in age; the same 

 South American Forniicariidw are black if they are males, but of the 

 color of a dead leaf if they are of the gentler sex. The male Bobolink 

 is bright black and white, and is strikingly beautiful in July. In August 

 the same male Bobolink cannot be distinguished from his homely wife. 

 These are striking exceptions to general rules, but they are also as uni- 

 versal as the rules themselves. They form a part of them, and in time 

 we come to know them, and cease to regard them as at all remarkable. 



" In this connection I take no notice of the anomalies now known as 

 albinisms and melanisms, whereby we hear of black birds that are white, 

 and of red squirrels that are black. That is another form of anomaly 

 exceedingly curious, and which 'no feller can find out,' but which has 

 no connection with my present subject. That is occasional — erratic like 

 a comet. My case is like a fixed star, unvarying in its ever varying 

 eccentricity. We have in the southern portions of the United States 

 a species of heron known to our authors as the Reddish Egret. The 

 head and neck are of a chestnut-brown, and its body is of a grayish blue. 

 In scientific language it is the Bemiegretta rufa or rufeseens. Its exist- 

 ence has been known in the scientific world since 1783.* We have in 

 precisely the same localities another form, identical in size, that is of a 

 uniformly pure white color. This bird was first described in 1828 by 

 Bonaparte, as the Peale's Egret Heron, and was for a while regarded as 

 a distinct species. 



" Mr. Audubon, in his excursions to Florida, was led to the conclusion 

 that these two forms of heron were, in reality, one and the same species, 

 and that the white Peale's Egret is only the young of the Reddish Egret; 

 and nccordingly we find in his great work, and again in his smaller 

 edition, these two forms given as the young and the old birds of one 

 and the same species. This conclusion was formed on a hasty basis, 

 and was not confirmed by subsequent observations. Even Mr. Audu- 

 * By a typographical error, printed " 1874" in the original. 



