I agree with Phil. I live in the French Alps not far from Geneva,at one of the local reserves just on the Swiss side of the border, there's been a House/Tree Sparrow hybrid which calls like a House Sparrow, mixes with House Sparrows, but has a chestnut crown and the 'shadow' of a cheek spot.
Italian Sparrow is slowly colonising Alpine villages in Southeast France near the Italy/France border, we've had a male around our place for 4 years now, breeding with a House Sparrow female, so we've a few male hybrids domesticus/italiae, they have thin white super before and after the eye, reduced amount of grey on the head with brown flecks, more chestnut at the rear of the head than is typical for domesticus, whiter cheeks and underparts and 'warmer/brighter' upperparts.l attach a couple of photos to demonstrate . First photo is the hybrid, second one the 'pure' Italian(as it were!)