There were THOUSANDS of Chen geese at Merced NWR the Saturday morning I was there, and they would go up in huge clouds in the distance. This was a fly-up group of several hundred on the water by the auto tour -- I imagine there were some Ross's Geese in there, but I could never identify any in the flock, which was facing away from me when it was on the water. I did see quite a few with the "grinning mark" characteristic of Snow Geese.