Italian Sparrow, Italy.
"Passer hispaniolensis italiae"

The Italian Sparrow causes a problem for several birding authorities: no-one agrees on exactly what it is. Some believe it to be a stable hybrid between Spanish and House Sparrows (Passer hispaniolensis x domesticus), some that it is separate species (Passer italiae) and others that it is a subspecies of the Spanish Sparrow (Passer hispaniolensis italiae). The latest scientific research goes with the latter idea (which causes some taxonomic problems of its own). They look superficially similar to both Spanish and House Sparrows, which probably caused the confusion originally. Photos 1 and 2 are males, 3 and 4 are females.
 

1-4: River Arno, Firenze (Florence), Italy, 22/09/2008.