Spanish sparrow
The taxonomy of the house sparrow and its Mediterranean relatives is complicated. The common type of "willow sparrow" is the Spanish sparrow, which resembles the house sparrow in many respects. It frequently prefers wetter habitats than the house sparrow, and it is often colonial and nomadic. In most of the Mediterranean, one or both species occur, with some degree of hybridisation. In North Africa, the two species hybridise extensively, forming highly variable mixed populations with a full range of characters from pure house sparrows to pure Spanish sparrows.