the eye). The juvenile resembles the adult female, but young males are more chestnut from an early age, with a trace of a black bib on the chin. In 1898, ornithologist Boyd Alexander reported that adults begin moulting in early February, and some birds were still in moult by late May. The Iago sparrow's vocalisations include calls, varying between the sexes, elaborations of these called 'songs', and an alarm call. Calls are chirps, somewhat similar to those of other sparrows, the usual version made by males described as a "twangy" or , and that of females described as a "more sibilant" . The song is a long, elaborated series of call notes, and is made by breeding males in their nests. An alarm call like that of other sparrows, transcribed , is also used. Taxonomy The Iago sparrow was first collected by Charles Darwin during the first stop of the second voyage of HMS Beagle at the island of Santiago (St. Iago). It was described for him in 1837 by zoologist John Gould, in 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, where it remains. 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). These birds were usually treated as distinct species until Reginald Ernest Moreau, writing in the 1962 Check-list of the Birds of the World, lumped the Iago sparrow and the mainland rufous sparrows as the single species Passer motitensis. This taxonomy was followed frequently until J. Denis Summers-Smith, a world authority on sparrows, argued in the 1980s that the Iago sparrow's many differences in morphology and behaviour, and separation from the other rufous sparrows by about , are sufficient grounds for species status. Studies of mitochondrial and nuclear DNA have since suggested it may be a close relative of the house sparrow and the Spanish sparrow and not the rufous sparrows. French ornithologist Émile Oustalet described a specimen from Branco as