information:extraction
Subspecies

A large number of subspecies have been named, of which 12 were recognised in the Handbook of the Birds of the World. These subspecies are divided into two groups, the Palaearctic P. d. domesticus group, and the Oriental P. d. indicus group. Several Middle Eastern subspecies, including P. d. biblicus, are sometimes considered a third, intermediate group. The subspecies P. d. indicus was described as a species, and was considered to be distinct by many ornithologists during the 19th century.

Migratory birds of the subspecies P. d. bactrianus in the P. d. indicus group were recorded overlapping with P. d. domesticus birds without hybridising in the 1970s, so the Soviet scientists Edward I. Gavrilov and M. N. Korelov proposed the separation of the P. d. indicus group as a separate species. However, P. d. indicus group and P. d. domesticus group birds intergrade in a large part of Iran, so this split is rarely recognised.

In North America, house sparrow populations are more differentiated than those in Europe. This variation follows predictable patterns, with birds at higher latitudes being larger and darker and those in arid areas being smaller and paler. However, how much this is caused by evolution or by environment is not clear. Similar observations have been made in New Zealand and in South Africa. The introduced house sparrow populations may be distinct enough to merit subspecies status, especially in North America and southern Africa, and American ornithologist Harry Church Oberholser even gave the subspecies name P. d. plecticus to the paler birds of western North America.