134 PROCEEDINGS OF THE ACADEMY OP 



parts, — the transverse bands being broadest on the flanks and under tail and 

 wing coverts, narrowest in the middle of the belly. The primaries are 

 brownish black, narrowly tipped with rufous, their shafts yellowish, their 

 inner webs fading basally into white. The tail has the same coloration as 

 the wings. The central feathers project about three-fourths of an inch. 



As the bird above described grows older, the bill and feet become stouter, 

 the cere better developed ; while the rufous everywhere gives way to the 

 darker color. No special stage can be characterized, however, until the 

 rufous is far outweighed by the dusky. Then we have — • 



(No. 18652). — Size and general proportions nearly those of the adult. Bill 

 and cere perfectly formed ; feet mostly black, but with some yellow blotches. 

 The upper parts are unadulterated with any rufous bars ; the deep brownish- 

 black pileum has appeared, and the sides of the neck have obtained their 

 yellow nuance, which contrasts conspicuously with the fuliginous background. 

 Evidences of immaturity, however, are found on the under parts, where the 

 dark color is mixed with illy-defined transverse bars of ochraceous. Rufous 

 is also found at the bend of the wing, and on the uader wing and tail coverts. 

 The primaries are still whitish baso-externally, as are also the rectrices. The 

 central rectrices project 2^ inches, and have the tapering form of those of the 

 adults. 



By the disappearance of the little rufous mentioned above, we have arrived 

 at a very marked and decided stage, — viz : 



(No. 20362). — With the size and proportions of the adult. Wholly deep 

 dusky ; darker and more plumbeous superiorly ; lighter, and with a fuliginous 

 tinge inferiorly ; the pileum quite black ; the latero-nnchal yellow, well 

 pronounced ; the remiges and rectrices quite black ; feet black. 



Having reached this perfect dusky stage, we will go back again to the 

 young plumage first characterized, and show how specimens occasionally 

 seem to proceed at once towards the adult condition with the white under 

 parts. For example — 



(No. 2754). — The juvenility of the specimen is attested by its small size, 

 delicate bill and feet, little projection of the central rectrices, general molli- 

 pilose condition of plumage, &c. The rufous of the very young bird, instead 

 of giving way everywhere to dusky, yields to this color only on the upper 

 parts and crown ; on the sides of the head, neck, and the whole under parts, 

 whitish being the predominating color, — the continuity of this last being 

 interrupted by indistinctly marked dusky bars. The yellow of the sides of 

 the neck has not yet appeared. There is the same white space on the bases 

 of the wings and tail as exists on the very young. The central tail feathers 

 only project about Ij inches. 



By an attentive consideration of the preceding facts, it will be evident that 

 we have found the same very young plumage to change gradually through 

 one series of specimens into the fusco-unicolor state ; through another series 

 into a stage which tends to pass directly into the normal plumage of the fully 

 adult bird, without going through this dusky epoch. What can we deduce 

 from this perplexing fact? Does one sex assume this dusky plumage at a 

 certain age, and the other not? Does this dusky state constitute the normal 

 adult plumage of one sex ? Is it a seasonal feature, which both sexes return 

 to at certain periods in each year? — or, finally, does it constitute a purely 

 accidental, but constant variety? Authors of weight are divided on each of 

 these points. 



I reject entirely the last hypothesis, — viz : that some birds attain to thia 

 dusky stage and retain it during their lives, though they may have sprung 

 from normally colored parents, and have normally colored progeny. What- 

 ever age or season, or whichever sex this state of plumage indicates, I think 

 there can be no reasonable doubt that it is a normal and constant stage which 

 every individual of one (or both ?) sexes passes through or attains to, in its 



[May, 



