Those look like starlings to me. A flock about that big has a winter roosting site at the end of our street in a big cottonwood tree. You should hear the dawn chorus. It’s amazing !
About 5 years or so ago I had found a waterbird dead by the electric fence, thought it got hung up or something and was killed. I picked it up and thew it in the garbage. In less than a week I came down with the damn west nile virus.