To E. W. V. Harcourt   9 May [1856]

Sir

I do not know whether you will allow a strong taste for Natural History as some excuse for the liberty I take in writing to you & begging the favour of a little information. Having visited during the voyage of H.M.S. Beagle & collected at many islands, I am greatly interested in their natural History, & I have lately seen your list, with valuable remarks, of the birds of Madeira.—¹ I observe in your list a considerable number of occasional visitants, & I am for reasons, with which I will not trouble you, very curious to hear, whether you have any idea how frequently such stray wanderers visit the island. Whether, for instance, the same wanderer has been seen more than once. If I knew at what date the list was begun, then I could, on the supposition that the same species had never arrived more than once, get some very rude idea whether on an average one or two wandering Birds arrived in the course of a year. Might I ask whether the wanderers have been observed at the times of migration of the Europæan species?— I presume there can be no sort of evidence to lead to the belief that wanderers of the same species of Birds, which permanently inhabit the island, are ever blown from the continent to Madeira.—

I suppose I am right in inferring from your list that no regular migratory Birds inhabit Madeira.—²

If you will forgive this rather long series of questions, & be so kind, at your leisure, to afford me any information, I shall feel very much obliged, & I beg to remain | Sir | Your obliged servant | Charles Darwin