A few years ago I went to a gym where the cardio machines looked over a pond. During that winter there was a flock of geese. I got to where I'd watch them while I did my cardio workout.
There is always a goose on all four sides always standing looking outward from the group. They don't eat, goof off, all they do is watch and warn. About 30 minutes later another goose will come and take their place. If one is injured one or two geese will stand with that goose. They are an interesting bunch to work.