I have noticed that they sometimes have a relationship with pigeons.
When I lived in Birmingham, there was a pair of them, a magpie and a wood pigeon, that always foraged together. I saw them every morning, in our garden and on the roadside verge at the front.
Thought that this was a one off, but 200+ miles away in Cornwall where I now live, I have seen the same behaviour.
Whether it is just an opportunistic pigeon following a magpie, I don't know for sure.