While staying in Evergreen, Colorado, one of our favorite things to do is to take walks around the lake. During one of the morning walks around Evergreen Lake, we happened to notice a bird sitting out by the only spot that had not frozen over. Once we were able to get closer, we could see it was a goose, not a duck as we originally thought. Shortly after we came in for a closer view, so did a group of Ravens. They proceeded to try and drive the goose off his choice spot by the open water. At first, he stood up and faced them directly and then decided that a better tactic would be to sit and ignore them. I was surprised at how good he was at that. When he stood again, the ravens must have thought he meant business because they flew off and waited on the edge for the goose to leave.
This link describes the different names that a group of ravens go by. I would say an Unkindness of ravens definitely describes this particular bunch.