No interactions present.
While there are Black-headed Gulls in this photo, there is also a significant number of Common Gulls present - nearest bird centre is this species - note the black wing-tips along with the white mirrors and plain yellow bill.
Thanks Dave, there were quite a few different types of Gulls gathered together in the field. Just wish I had a good telephoto lens.
Lat/Lng: 54.9, -2.1
OS grid ref: NY9856