Gulls (along with ducks, geese and other water birds) gather by the island in the Severn at Bridgnorth.
This is a lesser black backed gull.
Here is an adult black-headed gull. The first picture is of a younger individual of the same species.
The island itself, with the cliff leading up to High Town in the background. When I took this picture, the other water birds all seemed to have headed off elsewhere.