House Sparrow (Passer domesticus) - HBW 14, p. 793

Taxonomy: Fringilla domestica Linnaeus, 1758, Sweden.
Presumed to have evolved from sparrow population that was trapped in Middle East during last Pleistocene glaciation (25,000-15,000 years ago). Forms a superspecies with P. italiae and P. hispaniolensis, and the three sometimes considered conspecific. Hybridizes with former in N Italy and with latter in SE Europe (Balkans), NW Africa, and Cape Verde Is (on São Vicente, where introduced), and evidently with P. castanopterus in Somalia; hybrids with P. montanus regularly reported, particularly where one of the two species rare and presumably has difficulty in finding a mate of its own species. Races form two groups, "nominate (or Palearctic) group" (also with balearoibericus, tingitanus, niloticus, biblicus and persicus) and "indicus (or Oriental) group" (also incorporating rufidorsalis, hyrcanus, hufufae, bactrianus and parkini), these groups intergrading where ranges meet. Migratory race bactrianus of the "indicus-group", and hence indicus itself, considered by some authorities worthy of full species rank, largely on grounds that it does not interbreed with resident nominate race (which has spread to C Asia in the last century) as well as differences in morphology and ecology; this, however, seems unsustainable as indicus intergrades with persicus, clearly a member of "nominate group"; lack of interbreeding seems more probably a temporal than a genetic effect. In North America, where introduced, birds from W USA described as race plecticus, supposedly paler than nominate, but differences apparently clinal; proposed race maroccanus (from Morocco) is synonymized with tingitanus. Nomenclature of introduced populations problematic, as many have differentiated sufficiently to be subspecifically separated from the parent stock; this certainly the case in North America, and also in S Africa (where some populations are derived from introduction of indicus from India that have interbred with smaller inoculum of nominate from Europe), and will obviously become an increasing problem as other introduced populations diverge. Twelve subspecies recognized.