Passer is a genus of sparrows, also known as the true sparrows. The genus includes the House Sparrow and Eurasian Tree Sparrow, some of the most common birds in the world. They are small birds with thick bills for eating seeds, and are mostly coloured grey or brown. Native to the Old World, some species have been introduced throughout the world.
The Spanish Sparrow or Willow Sparrow (Passer hispaniolensis) is a passerine bird of the sparrowfamily Passeridae. It is found in the Mediterranean region and southwest and central Asia. It is very similar to the closely related House Sparrow, and the two species show their close relation in a "biological mix-up" of hybridisation in the Mediterranean region, which complicates the taxonomy of this species.