skip to content

Darwin Correspondence Project

From Edward Blyth   [after 24 February 1867]1

years ago, and ⁠⟨⁠ 12 line excised⁠⟩⁠ remarks were quite forgotten by myself.2 I have not much now to comment upon them. I remember that Gould assured me about the difference of sexes in the common Gallinule, saying that the female is both larger and handsomer—colouring; but a much more decided instance3 [missing section of unknown length]

The fact stated by Gould of the extraordinary development of the trachea in the female only of Rhynchea australis, is the more remarkable that nothing of the kind occurs in the female of R. bengalensis; yet the birds are scarcely distinguishable externally, except that the Australian species has shorter toes.4 [missing section of unknown length]

though more slowly in the females, the only difference being that the fully mature females are duller-coloured on the back.

In a remarkable hornbill (Aceros nipalensis) inhabiting the S.E. Himalaya and the mountains of Burma, the female (or what from analogy I presume to be such) has wholly black plumage with white tail-tip, whereas the (presumed) male has the head, neck, and lower-parts bright ferruginous.5 Now in a nestling bird of this species in the Calcutta museum, the colouring is that of the (presumed) male, and possibly the sexes may be thus distinguished from the first. They are slightly so in the British blackbird and stonechat;6 and in a parrakeet very common in Burma (Palæornis javanicus), the young from the first are conspicuously distinguishable by the male having the upper mandible coral-red, while in the female it is black; this continues for the first year at least, after the adult plumage has been attained, but finally the upper mandible of the female becomes red as in the male, and I have witnessed the change in a caged bird, besides that I have seen many specimens with the bill in process of change.7

By Ardeola I meant Ardetta, which is the name now given to the little bittern of this country and its immediate congeners.8 In Ardeola, of which the European squacco heron (A. ralloides ) is characteristic, there is very great difference in the summer and winter plumage, the latter being so similar in some of the races that they cannot be told apart, whilst in summer dress they are strongly distinguished.9

The seasonal change in the plovers and sandpipers is completed in India before the several species leave the country for their breeding haunts. We really know very little of the southern

CD annotations

1.1 years … instance 1.4] crossed blue crayon
2.1 trachea in the female 2.2] underl blue crayon
3.1 though … on the back. 3.2] ‘P’ top of page, blue crayon ‘(Case of Parrots Bill)’ end of para, pencil
3.1 though … process of change. 4.12] crossed pencil
3.7 (Palæomis javanicus),] ‘P’ in margin, blue crayon
4.12 change.] ‘3’ circled blue crayon, end of para
6.1 The … southern 6.3] crossed pencil
6.2 We … southern 6.3] crossed blue crayon


The date is established by the relationship between this letter and the letter from Edward Blyth, 24 February 1867 (Correspondence vol. 15).
Blyth refers to two pages of galley proofs of a translation of Georges Cuvier’s Règne animal with footnotes by Blyth (Cuvier 1840 and 1849, pp. 158–9; these are pages 146 and 147 in Cuvier 1859). The pages, with annotations by both CD and Blyth, are in DAR 84.1: 179–80. When CD asked some questions about Blyth’s editorial remarks on these pages, Blyth asked CD to send the pages because he could not remember them (see Correspondence vol. 15, letter to Edward Blyth, 23 February [1867] and letter from Edward Blyth, 24 February 1867).
In his footnote, Blyth had referred to the ‘typical state’ of plumage in birds, which was usually only attained by adult males, but in the common gallinule, it was attained only by the adult female (Cuvier 1840 and 1849, p. 158). Blyth refers to John Gould.
Rhynchaea australis (‘Rhynchea’ is a misspelling) is a synonym of Rostratula australis, the Australian painted snipe; Rhynchaea bengalensis is a synonym of Rostratula benghalensis, the greater painted snipe. Tracheal elongation in females is described by John Gould in Gould 1865, 2: 275. CD scored the passage on the trachea in his copy of Gould 1865 (see Marginalia 1: 340). In Descent 2: 202–3, CD cited Blyth and Gould on the sexual differences in the trachea of these birds.
Aceros nipalensis is the rufous-necked hornbill.
In Descent 2: 219 and 220 n. 49, CD referred to the male and female young resembling, respectively, the male and female adults of the blackbird, ‘Turdus merula’, and the stonechat, ‘Saxicola rubicola’.
Palaeornis javanicus is now Psittacula alexandri fasciata, a subspecies of the red-breasted parakeet. In Descent 2: 179, CD cited Blyth’s description of the differences in the colour of male and female upper mandibles. Modern descriptions differ from Blyth’s (see Juniper and Parr 1998, p. 414).
Ardetta minuta, mentioned on p. 158 of the galley proof (see n. 2, above), is now Ixobrychus minutus, the little bittern. CD crossed out ‘Ardeola’ and added ‘Ardetta’ in the margin of p. 158 of his copy of the galley proof. CD cited Blyth’s notes to Cuvier 1840 and 1849 in Descent 2: 180 n. 29.
CD discussed the summer and winter plumage of several species of Ardeola (pond herons) in Descent 2: 190.


Cuvier, Georges. 1840. Cuvier’s animal kingdom: arranged according to its organisation. Mammalia, birds, and reptiles by Edward Blyth. The fishes and radiata by Robert Mudie. The molluscous animals by George Johnston. The articulated animals by J. O. Westwood. London: Wm. S. Orr and Co.

Cuvier, Georges. 1859. The animal kingdom, arranged after its organisation … by the late Baron Georges Cuvier. Translated and adapted to the present state of science. Mammalia, birds, and reptiles by Edward Blyth. The fishes and radiata by Robert Mudie. The molluscous animals by George Johnston. The articulated animals by J. O. Westwood. A new edition with additions by W. B. Carpenter and J. O. Westwood. London and Edinburgh: A. Fullerton & Co. [Reprint of Cuvier 1849, with added plates.]

Gould, John. 1865. Handbook to the birds of Australia. 2 vols. London: the author.


Sexual differences in bird species and seasonal variation in plumage.

Letter details

Letter no.
Edward Blyth
Charles Robert Darwin
Sent from
Source of text
DAR 84.1: 105–6
Physical description
AL inc

Please cite as

Darwin Correspondence Project, “Letter no. 6403,” accessed on 1 October 2023,

Also published in The Correspondence of Charles Darwin, vol. 18 (Supplement)