A couple of weeks ago I had a dental appointment in Macclesfield. Running a little early, and afforded the opportunity to drive somewhere in the car, I stopped off at a very frozen Redesmere on the way.
I'd say the mere was 85% frozen with thick ice. This meant that the gulls were close in and resting on the ice, while anything else was distant on the very small open patch of water. It's much easier to check out the gulls if they are not bobbing around on the water.
The Black-headed Gulls here were plentiful, with this one particular bird in the centre already in full breeding hood. The legs were also noticeably darker.