This is only a small fraction of the herd of swans that assembles on the estuary of the Tweed over the summer. It is common to see more than fifty together, and not that unusual to see a hundred or so, although when the numbers get that large it's hard to keep count of a constantly swimming target. They gather on the estuary during the moulting season in July and August because, apparently, they can't fly while their old flight feathers are being shed, so they need a safe place to hang out while the new feathers grow. They don't all go away in the winter though, there are always a fair few swans around on the river and on the sea just offshore.
And trust me, you don't want to get on the bad side of a swan. They come up to chest height on a human adult and that beak looks pretty worrying when it gets that close to your face. The closest encounter I ever had with one was during the heavy snow a couple of winters back. White swan sitting in white snow equals total camouflage. The first I knew about it was when a large angrily flapping creature rose up in front of me just before I stood on it. I was definitely more scared than it was. I didn't slow down until I got to the far side of the bridge.