The wet fields are attracting the corvids - not sure we have ever seen so many on our land (and there were a lot more than shown). We are guessing that invertebrate life is up near the surface and so there are rich pickings to be had.
We don't mind the corvids, as long as they leave our young birds and lambs alone in the spring..... known for pecking out the eyes of dead (or even trapped but still alive) livestock and as we know from living at Lamorna, taking whole chicks and ducklings, they are NOT always the farmer/ smallholder's best friend!!