Iago Sparrow - Taxonomy

Taxonomy

The Iago Sparrow was first collected by Charles Darwin during the first stop of the second voyage of HMS Beagle at Santiago island, then called St. Jago. It was described for him by zoologist John Gould, in the 1837 volume of the Proceedings of the Zoological Society of London, and given the name of Pyrgita iagoensis. By the time Gould wrote The Zoology of the Voyage of H.M.S. Beagle with Darwin and three other zoologists in 1841, he had placed the Iago Sparrow in the genus Passer, in which it has since been placed. The genus, among the sparrows of the Old World in the family Passeridae, also contains at least 20 other species, among them the House Sparrow and Eurasian Tree Sparrow. Within its genus, the Iago Sparrow has been considered one of the African 'rufous sparrows', a group which also includes species such as the Great Sparrow (Passer motitensis). Treatments of these birds as distinct species were usually followed until Reginald Ernest Moreau, writing in the 1962 The Check-list of the Birds of the World, merged the Iago Sparrow and the mainland rufous sparrows as Passer motitensis. This taxonomy was followed frequently until J. Denis Summers-Smith argued in the 1980s that the Iago Sparrow's many differences in morphology and behaviour, and separation from the other rufous sparrows by about 5,000 kilometres (3,100 mi) are sufficient grounds for species status. Studies of mitochondrial and nuclear DNA further suggest it may be a close relative of the House Sparrow and the Spanish Sparrow, rather than the rufous sparrows.

French ornithologist Émile Oustalet described a specimen from Branco as a separate species Passer brancoensis in 1883, which was recognised as a subspecies recognised by W. R. P. Bourne, who claimed to observe differences between birds from different islands. According to Bourne, birds of Passer iagoensis iagoensis on more wooded islands in the south are darker and larger, and also behave more like House or Spanish Sparrows, competing with them better in human-altered habitats. He later wrote that the variations he saw comprised two clinal trends, of increasing darkness towards the south, and of smaller size further from the continental coast. Charles Vaurie, examining differences in plumage and measurements of specimens in major museums, did not find any significant variation, and Vaurie and Summers-Smith both did not recognise any subspecies.