This looks like a crow to me – mind you so do all the other black birds – except the blackbird of course. This guy was on his own in the field. There was another black bird quite a distance away – certainly not within caw-ling distance. At one time, in my slothful youth, when I noticed one of these guys pacing along the grass verge as I drove past in the car – I always imagined that they had probably dropped a contact lens somewhere and were doing their best to find it with only one eye. On closer acquaintance I now know that this is not the case. Nor are they lost in deep philosophical ruminations.
No, they are just grumpy old sods that find other people irritating.