The change from echo to eques was made following my recommendation to David Donsker, editor of the IOC World Bird List. Here is what I wrote to him in December:
Brisson (1760), Buffon (1779), Mauduyt (1784), and Levaillant (1805) described a Psittacula parakeet from Réunion (it's likely several live birds reached Paris in the late 1700s) indistinguishable (from their descriptions) from P. echo, which Boddaert (1783) named Psittacula eques. No skins or fossils exist (an enigmatic skin in Edinburgh may represent P.eques, but its provenance is uncertain, and the bird may have originated in Mauritius), but there is a very fine illustration of this bird by Barraband in Levaillant (1805). No distinct differences between eques and echo are apparent in Barraband's illustration, indicating that eques and echo were conspecific, perhaps not even subspecifically distinct.
A. Newton and E. Newton named the Echo Parakeet Palaeornis echo in 1876 (Ibis, 1876, p. 284):
"A smaller species of Parrot [than Lophopsittacus mauritianus] - commonly known as Paleornis eques - still survives in Mauritius, but its numbers are gradually failing, though in the district of Grand Port, where the monkeys have been thinned, it seems to be enjoying a transient prosperity...
Here it is to be remarked that the specific term eques, conferred by Boddaert on the subject figured in the 'Planches Enluminées' (No. 215), properly belongs to the Parrakeet of Réunion - the bird there represented being called "Perruche de l'Ile de Bourbon," whence De Buffon (Hist. Nat. Ois. vi. p. 144) expressly says it was brought, identifying it also with the "Perruche à collier de l'Isle de Bourbon" of Brisson (Orn. iv. p. 328, pl. xxvii. fig. 1), who likewise states that it is found there. It no longer inhabits Réunion, and whether a specimen from that locality anywhere exists is not known to us. Judging from the general dissimilarity of the avifauna of that island and of Mauritius, we should be inclined to suppose that each had its peculiar Palaeornis; and, in the event of this being found to be the case, we would venture to suggest the term echo being applied to the Mauritian bird, which, no doubt, answers in nearly all particulars to the true eques."
A footnote, in Greek and Latin, explains the derivation of the word echo:
Ἠχὼ, nympha quaedam, imitatrix equitis - sc. Narcissi. Ov. Meta,. iii. 380.
Psittacula echo was therefore named after the wood nymph Echo, because it was an imitator of eques. Although no type specimen is named, on the previous page, Newton mentions that Finsch's description of eques in v.2 of his Die Papageien were based on specimens in Cambridge collected in Mauritius. Note that Newton & Newton named the taxon on the supposition that it differed from eques.
If these parrots are conspecific, then Psittacula eques Boddaert, 1783 has many years priority over Psittacula echo (Newton & Newton 1876). Although Knox & Walters (1994) listed Mauritius Parakeet as Psittacula eques echo, Hume (2007) treated them as separate species. Cheke and Hume (2008) however treated them as conspecific.
-Rick Roe
