# To H. B. Tristram   4 June 1868

Down. | Bromley. | Kent. S.E.

June 4 1868

Dear Sir

Although I have not the pleasure of your personal acquaintance, I hope & think that you will excuse the liberty which I take in writing to you. I have lately read some papers formerly published by you in the Ibis, in which you specify various birds coloured so as to resemble the desert.1 Now I shd be greatly obliged if you would inform me whether with these birds the two sexes closely resemble each other, & whether, as far as known, the young resemble the adults. As I did not think that this subject wd specially concern me, I unfortunately returned the vols without making an extract   Therefore I shd be much obliged if you wd give me a reference. I read, about a year ago, with lively interest your work on the Sahara, & if I am not mistaken there was in it a similar discussion on the colouring of desert-birds.2 If it wd not cause you too much trouble, I shd very much like to be permitted to quote from you some such sentence as follows “Mr Tristram informs me that about … birds, inhabitants of the Sahara, are coloured in a protective manner so as to resemble the surrounding desert.3 In all these species (or in $\frac{2}{3}$ or $\frac{1}{2}$ &c (?)) the 2 sexes in the adult state, & the young resemble each other; yet about $\frac{1}{2}$, $\frac{1}{3}$, or $\frac{1}{4}$ (?) of these birds belong to groups in which the sexes usually differ to a certain extent in colour”.

I hope that you will excuse me troubling you & if in your power grant me this favour.

Pray believe me dear Sir | yours faithfully | Charles Darwin

## Footnotes

Tristram had written a series of articles titled ‘On the ornithology of northern Africa’ for the journal Ibis (Tristram 1859–60).
In The great Sahara: wanderings south of the Atlas mountains (Tristram 1860, pp. 389–404), Tristram had included an appendix in which he listed the birds of the Sahara that he had observed, and noted the protective colouring of several of these birds.
For Tristram’s reply to this letter, see Correspondence vol. 16, letter from H. B. Tristram, 1 July 1868. Tristram noted that twenty-six species of Saharan birds had protective colouring and that, while thirteen species had sexual differences in colouring, the differences were confined to the under-surface of the bird, so that both sexes in these species could still benefit from the protective colouring of the upper surface of their bodies. CD cited Tristram on protective colouring in Saharan birds in Descent 2: 172, 224–5.

## Letter details

Letter no.
DCP-LETT-6227F
From
Charles Robert Darwin
To
Henry Baker Tristram
Sent from
Down
Source of text
Private collection