The Spanish sparrow or willow sparrow (Passer hispaniolensis) is a little bird of the sparrow family Passeridae.
In appearance and behavior very similar to the house sparrow, which is confused by inexperienced observers.
Unlike the Sparrow, the black spot on the breast is much larger.
It also forms noisy colonies.
In this photo are male and female Spanish sparrows.
They can most easily be observed under the stork nests where they make their colonies.
Wow, they sure do look like P. domesticus! Without the context of your post, I definitely would have assumed that was a house sparrow. After a closer look, I do see the larger black spot on the breast that distinguishes it. Very interesting, I enjoy learning about bird species outside of the USA :)
These sparrows are also not typical of Bulgaria :)