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Darwin Correspondence Project

From Edward Blyth   4 October 1868

7 Princess Terrace, | Regent’s Park,

Octr. 4 /68

Dear Mr. Darwin,

With respect to your first question, asking for more illustrations of the fact of one sex only differing in certain kindred races (or species) of birds, I cannot do better than refer you to the paper indicated in my last; for I remember that there are one or two cases mentioned there that I do not think that I have since mentioned: e.g. Tephrodornis and Thamnobia.1

Next, about cuckoos. It is the barred upper rather than the “under surfaces” which you must mean. Well, then, there is the hepaticus plumage of C. canorus, rare in this species and probably confined to the female sex; it being a repetition of the barred nestling dress.2 In C. striatus (apud Schlegel, vide “Ibis,” 1866, p. 359), this hepatic plumage is more common, and still more so in C. poliocephalus (which is figured in this dress erroneously as C. himalayanus in Gould’s “Century of Himalayan Birds”).3

In C. Sonneratii this nestling-like hepatic colouring is permanent, there being no ashy phase as in the others.4 Thirdly, the first plumage of the crossbills is striated, very like that of a redpole, or of a hen siskin,—and the same remark applies to the young goldfinch and greenfinch, which species are streakless when adult. Does not Yarrell figure the young of the crossbill in his ‘British Birds’?5

The turacos constitute the exclusively African family Musophagidæ, comprising Musophaga, Turacus, (see Corythaix), Schizorhis, and (in my opinion, but as a distinct subfamily,) Colius. Musophaga and Turacus are united by Schlegel, and these are the birds to which I especially referred as “turacos”.6 However long ago I ventured upon the remark that the sexes are alike in these three families (Musophagidæ, Capitonidæ, and Rhamphastidæ, the two latter being very nearly allied), it still holds to the best of my information, unless there may be an exception or two in the S. American genus Capito, about which consult Sclater.7 In fact you had better ask him in the following words to prevent any confusion

—“Do you know of any Musophagidæ, Rhamphastidæ, or Capitonidæ, (inclusive of Mægalæmidæ), in which the sexes differ in plumage”?8 The name Bucco formerly included the Capitonidæ, but is now transferred to the very distinct S. American group formerly styled Tamatia with its kindred genera—9

Yours very truly, | E Blyth

CD annotations

1.1 With … Thamnobia. 1.5] crossed blue crayon
3.1 In C. Sonneratii] opening square bracket blue crayon
3.1 In … permanent,] scored blue crayon
3.2 Thirdly, … ‘British Birds’? 3.5] enclosed in square brackets blue crayon
4.1 The … sexes 4.5] crossed ink
4.5 are alike … confusion 4.9] crossed blue crayon
5.1 —“Do you know] opening square bracket blue crayon; ‘for Sclater.—’ added blue crayon


Blyth refers to Blyth 1850, p. 223; see letter from Edward Blyth, 1 October 1868 and n. 2. CD’s letter to Blyth has not been found. Blyth mentioned species of each genus in Blyth 1850, p. 223.
There is a ‘rufous morph’ of the female Cuculus canorus (the common cuckoo) in which the upper parts are barred chestnut and blackish brown with the rump and upper tail-coverts plain rufous (Birds of the world 4: 554).
Cuculus striatus is now C. saturatus (the Himalayan cuckoo; see Junge 1956). Blyth adopted this usage from Hermann Schlegel (see Schlegel 1864, p. 7, and Blyth 1866–7, p. 359). Canorus poliocephalus is the Asian lesser cuckoo. The ‘Cuculus himalayanus’ is illustrated on plate 54 of John Gould’s A century of birds from the Himalaya mountains (J. Gould 1832).
Cuculus sonneratii is now Cacomantis sonneratii, the banded bay cuckoo (see Birds of the world 4: 559).
CD referred to these, and other, birds losing their striated plumage when adult in Descent 2: 184. Blyth refers to William Yarrell and Yarrell 1843–56: 2: 14.
A modern classification of the turacos, family Musophagidae, includes the genera Tauraco, Ruwenzori, Musophaga, Corythaixoides, and Crinifer; see Birds of the world 4: 488–506. For the difficult systematics of the family, see ibid., pp. 480–2, and Newton 1893–6, pp. 979–82. Colius, a genus of mousebirds, is now in the family Coliidae. For Hermann Schlegel’s unification of the turacos into the single genus Musophaga, see Schlegel and Westerman 1860. Blyth’s earlier reference to turacos has not been identified.
The families Capitonidae (barbets) and Rhamphastidae (toucans) are now both in the order Piciformes, while the Musophagidae are in the order Cuculiformes (Birds of the world, vols. 4 and 7). The sexes are not alike in most species of Capito (ibid. 4: 213–14). Blyth refers to Philip Lutley Sclater.
Blyth may refer to what is now the subfamily Megalaimatinae, in the family Capitonidae (Birds of the world 7: 198–200). Newton 1893–6, pp. 28, referred to the subfamily ‘Megalaeminae’ in the family Capitonidae. In Descent 2: 177, CD wrote that Sclater informed him that both sexes were brightly coloured and alike in all species of ‘Musophagae’. No letter on the topic between CD and Sclater has been found.
Some nineteenth-century systematists placed the puffbirds of South America (now Bucconidae, including Bucco) in the family Capitonidae. Tamatia was an early genus name among the puffbirds, but is no longer in use. See Newton 1893–6, 3: 749–50, Birds of the world 7: 102–3, 140.


Replies to CD’s questions on sexual differences in birds.

Letter details

Letter no.
Edward Blyth
Charles Robert Darwin
Sent from
London, Princess Terrace, 7
Source of text
DAR 84.1: 100–2
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 6409,” accessed on 27 June 2017,

Also published in The Correspondence of Charles Darwin, vol. 16