ARDEID.E — THE HEROXS — NYCTHERODIUS. 63 



have seen is an adult female from Mount. Carmel, Illinois. This specimen was shot from the nest, 

 and a perfectly developed egg taken from the ovary ; consequently there can be no doubt as to the 

 sex. In this specimen the plumbeous is throughout of a clear, fine grayish-blue tinge ; the rec- 

 trices, even, are dark bluish plumbeous (with a faint green reflection in certain lights), and are 

 distinctly bordered with plumbeous-Vjlue. This fine example is nearly matched by No. 17148, 

 National Museum, from the Tortugas, Florida (spring of 1800). The opposite extreme is nearly 

 represented by another adult female, but probably a younger bird, from the same locality, and 

 obtained at about the same time and under nearly the same circumstances. In this specimen the 

 plumbeous is everywhere much less bluish, and on the back and lesser wing-coverts is even very 

 much obscured by a smoky tinge ; the black stripes of the back and wings show a very strong 

 bottle-green reflection, which is not the case with other specimens examined ; the rectrices are 

 absolutely uniform slaty plumbeous, without paler edges. The head is marked and colored as 

 usual in fully adult specimens, and the forehead has a slight tinge of ochraceous anteriorly. A 

 specimen from Fort Brown, Texas (3836, March 10), is almost precisely similar. 



An adult, in nxiptial plumage (No. 67919), from the Talamanca district, Costa Rica, diff"ers 

 from other specimens in full plumage in having several blue-black feathers in the middle of the 

 crown. This specimen is also remarkable for its large size. 



Some specimens, apparently in their second year, resemlile adults in full plumage, except that 

 they lack the scapular and occipital plume.;, and that the black of the head, especially underneath, 

 is mixed with white feathers. Nos. 28062 and 67920 represent this stage. As a proof that the 

 brown tinge on the crown of this species has nothing to do with season or sex, but that, on the 

 contrary, if not an entirely accidental stain from foreign substances, it is rather a mark of im- 

 maturity, it may be stated that both these immature specimens have the ferruginous stain very 

 strongly marked, it being in the former specimen deeper than I have ever seen it in any adult, 

 and so dark in places as to appear of a dark sepia- or snuff-brown tinge. 



A younger stage of plumage than the above, and one which perhaps illustrates a change in color 

 of the feathers themselves, without an actual moult, is represented by No. 11892 (Tortugas, April 5). 

 In this, all the well-defined stripes and streaks of the first stage have become obliterated, but at 

 the same time the sombre coLjrs of this age are retained. The upper parts, including the scaimlar 

 flumes, lohich are not only present, hut well developed,^ are of a dark oily, sooty, brownish-gray, 

 with a faint green reflection in certain lights ; many of the feathers darker medially (especially 

 the wing-coverts and scapular plumes), the wing-coverts having well-defined pale margins. The 

 forehead and middle of the crown are rich .bro\\Ti, of a shade between cinnamon and sepia ; the 

 occiput uniform blue-black ; the malar region and throat streaked with blue-black and white. 

 The lower parts much as in the first plumage, but the stripes more indistinct. There are no 

 occipital plumes. 



From the above, we may reasonably infer that the assumption of the perfect adult plumage is 

 a very gradual process, and not accomplished at a single, nor solely by several moults ; but that 

 after each moult a gradual change in the colors of the feathers takes place, — a feet which is cer- 

 tainly established with regard to many birds. Those specimens in which the plumbeous is of a 

 clear, fine bluish cast are therefore to be considered the oldest individuals, and the more sombre 

 ones younger. 



In the Galapagos Islands is found a Nyctherodius which is said to be distinct from the common 

 species. This form we have seen only in the immature plumage, a description of which is given 

 below."- 



' It is probable that the species breeds in this plumage. 

 2 Xyctherodius pauper (Scl. & Salv.). 



" Kydicorax violaeeus," Darwix, Zool. Beag. III. Birds, 1S41, 128 (Galapagos). 

 "Ardea violacea," Sundev. P. Z. S. 1871, 125 (Galapagos). 



Nydicorax paiqjcr, Scl. & Salv. P. Z. S. May 12, 1870, 323, 327 (Galapagos). — Salvix, Trans. 



Zool. Soc. IX. ix. 1875, 498. 



Voimg $ , transition plumage : Head chiefly black, uniform on the sides of the pileum and occiput, 



the centre of the latter mixed with elongated light-brown feathers having darker mesial stripes. Stripe 



on side of the head, from the rictus over the ear, liglit tawny brown ; malar region blue-black, with a 



few narrow whitish streaks ; chin and throat more heavily streaked with white. Upper parts in general, 



