Murmuration

I am frequently observing an unusual murmuration in the early evening. The number of birds is not great, somewhere between sixty and one hundred. It starts with a smaller group but new arrivals quickly join in. The flight patterns simulate what larger groups attain with sudden changes of direction and altitude, BUT, these birds are not starlings: they are JACKDAWS.
They display like this over the field where are have been getting a last minute feed, they do not roost here but in local woods.