Last year, and into this, I talked about the cranes that flew into the area, and instead of continuing further south, overwintered here. It would appear that similar things are happening with Bewick's swans in the UK.
"Winters used to be colder, so when they came down from Russia they travelled all the way to Britain to be at a comfortable temperature,"
"But these days, winters are warmer, so when they come down, they arrive in Germany and the Netherlands, and they think, 'It's good here. I'll stay. I'll not bother to travel all the way to England.'
"And northern Germany now seems to be the main area for them to stop and spend the winter."
https://www.bbc.com/news/science-environment-67407574