a separate species Passer brancoensis in 1883, which was recognised as the subspecies Passer iagoensis brancoensis by W. R. P. Bourne, who claimed to observe differences between Iago sparrows 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 neither Vaurie nor Summers-Smith recognised any subspecies. Distribution and habitat The Iago sparrow is endemic to the archipelago of Cape Verde. It is common on most islands, excluding Fogo (from which it is absent) and Santa Luzia, Branco and Sal (on which it is scarce). The Iago sparrow is found commonly in a variety of habitats, including flat lava plains, coastal cliffs, gorges, and the edges of farmland, at altitudes of up to . It also occurs in settled areas and gardens, where it may overlap somewhat with the house sparrow, but usually not with the Spanish sparrow. The Spanish sparrow occurs in richer cultivated land with larger trees and villages, restricting the Iago sparrow to more arid cultivated land with smaller trees. In settlements where both the house sparrow and Iago sparrow occur, house sparrows tend to occupy the denser areas, while Iago sparrows are found primarily around trees and open spaces. In agricultural areas the Iago sparrow may do some damage to crops, mostly by eating buds and shoots. The Iago sparrow is highly common within its limited range, though its exact population is not known. Though the size of its range means it may be at risk to unpredicted changes in its environment, it is assessed as Least Concern by the IUCN Red List. In May 2013 four vagrant Iago sparrows were seen at Hansweert, in the Netherlands, having flown onto a ship as it passed by the island of Raso. Behaviour The Iago sparrow is gregarious while foraging and breeding. Outside of the breeding season, Iago sparrows are always in flocks, which may be of considerable size. It flocks with other birds, even warblers such as the blackcap and the Cape Verde