April 20, 1900.] 



SCIENCE. 



627 



parent height of the cliffs, if blasting of the 

 latter could be prevented. 



Professor Dodge described the similar trap 

 formations of Connecticut. 



After a vote of thanks to both lecturers the 

 meeting adjourned. 



Theodore G. White, 

 Secretary of Section. 



DISCUSSION AND CORRESPONDENCE. 



THE PLUMAGES AND MOULTS OF THE INDIGO 



BUNTING (Passerina cyanea). 



It is no new idea that the Indigo Bunting 

 changes color without moulting, but just as one 

 swallow does not make a summer, neither does 

 one bird make ' aptosochromatism ' an assured 

 fact. This, however, is what a recent writer 

 (Birtwell, Science, N. S., Vol. XI., Feb. 23, 

 1900) would have us believe, and yet there is 

 quite a different way of looking at his supposed 

 facts which suffer from the very ' individual 

 error and dogmatism' he deprecates in others. 

 He says " It is a singular fact that certain in- 

 dividuals have conceived the idea that a feather 

 once having passed its premature condition 

 (what may this be, please ?) is utterly discon- 

 nected with the vital system of the bird and 

 such individuals cling to this belief with a te- 

 nacity wonderful to behold . ' ' Doubtless it does 

 seem ' wonderful' to persons who would wave 

 aside all the careful observations that have 

 been made upon feather growth and feather 

 wear, and plumage generally, but possibly it is 

 not so wonderful as the strange things they see 

 just as soon as they watch a bird of striking 

 colors in a cage. It is well to understand some 

 elementary and fundamental facts that are self 

 evident before having recourse to theoretical 

 explanations, and lest Mr. Birtwell's conclu- 

 sions be taken too seriously, it is my present 

 purpose to first explain the plumage changes 

 which regularly occur in the wild Indigo Bunt- 

 ings and then show why observations upon 

 caged ones are open to doubt. 



The Indigo Bunting regularly moults twice 

 every year, differing in no wise in this respect 

 from many other species, and like some of 

 them it is also peculiar in requiring several 

 moults to reach the adult plumage. This is 



what usually takes place in highly-colored 

 species, and another peculiarity, if such it may 

 be called, is the retention at the time of one 

 moult of the feathers of certain areas until a 

 later period of moult, a mixture of older and 

 newer feathers in juxtaposition being the re- 

 sult. The key to the whole matter lies in un- 

 derstanding the principle of sequence of plumages 

 as I have called it (Auk., XVI., 1899, pp. 218- 

 220, pi. III. and XVII., 1900, pp. 34-43) which 

 is adequate to explain all parti-colored plu- 

 mages without recourse to theory. I regret, 

 that owing to unfortunate delays another article 

 which explains the principle and its applica- 

 tion at more length is still in press, so that it is 

 not at present available for reference. 



To understand clearly the successive stages 

 of plumage in the Indigo Bunting it is desir- 

 able to take them up in the order in which they 

 occur. 



Natal Down. — On hatching, the chick is 

 sparingly clothed with long downy filaments, 

 the precursors of the definitive feathers to the 

 apices of which they are attached. The down 

 varies very little among the many species of 

 Passerine birds. 



Juvenal Plumage. — This second stage succeeds 

 to the downy, part of the feathers being ac- 

 quired before the bird leaves the nest. Brown 

 is the prevailing color, paler below with streaks 

 most obvious on the breast. In females the 

 remiges and rectrices are wholly brown also, 

 but in males they usually have a greenish blu& 

 tint most marked in the tail and varying in in- 

 tensity according to the individual. The body 

 feathers are looser in texture than are those 

 of the next stage, assumedby the postjuvenal 

 moult which occurs in the latitude of New York 

 during August and September. 



First Winter Plumage. — The third stage of 

 plumage, commonly known as the 'autumnal,' 

 is similar to the previous one, the moult usually 

 involving only the body feathers. In males, 

 the feathers of the throat especially become 

 basally more or less tinged with dull blue, the 

 females remaining dull brown and gray. Some 

 males, however, assume by a more complete 

 moult a new tail and several, usually, five or 

 six, distal primaries which are nearly black and 

 distinctly edged with bright blue. Indisputable 



