In december of 2007, I was bowhunting on our place in Western OK in a blind alongside a huge alfalfa field. I saw a flock of about 20 birds come over the rise and down in front of me. I started calling them to try to get one in range, using feeding calls.
Then, on my left, I had another flock of about 15 birds come into the field.
When these two groups saw each other, they RAN toward each other and the two groups began duking it out like some kind of scene from Gangs of New York. It lasted about 10 minutes...then they just split up.
Oh, and neither group was interested in my call. Nearest I can tell, it was a territorial battle over feeding areas.