The Spanish Sparrow or Willow Sparrow (Passer hispaniolensis) is a passerine bird of the sparrow family 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.
The Spanish Sparrow is a rather large sparrow, at 15–16 cm (5.9–6.3 in) in length, and 22–36 g (0.8–1.3 oz) in weight. It is slightly larger and heavier than House Sparrows, and also has a slightly longer and stouter bill. The male is similar to the House Sparrow in plumage, but differs in its underparts heavily streaked with black, a chestnut rather than grey crown, and white rather than grey cheeks. The female is effectively inseparable from House Sparrow in its plumage, which is grey-brown overall but more boldly marked. The female has light streaking on its sides, a pale cream supercilium, and broad cream streaks on its back.
The two subspecies differ little in worn breeding plumage, but both sexes are quite distinct in fresh winter plumage, with the eastern subspecies P. h. transcaspicus paler with less chestnut.
The Spanish Sparrow’s vocalisations are similar to those of the House Sparrow. The male gives a call somewhat different from that of the House Sparrow when displaying at its nest. This call is a pair of strident, disyllabic chirps, similar to those of the House Sparrow, but louder and high-pitched, transcribed as chweeng-chweeng, cheela-cheeli. A similar call, softer and more like the House Sparrow’s tschilp, is used by birds arriving or departing at roosting sites. The Spanish Sparrow’s other calls are almost the same as those of the House Sparrow. A soft quer quer quer is given at the nest by mated pairs, a quer-it flight call is given by flocking birds, and a chur-chur-it call is given as a threat.