Out to Lunch

On the way home from a quick shopping trip I noticed a field providing lunch for - I'm not sure what - what is the collective noun for swans? Well I came up with:
a bank of swans
a bevy of swans
a whiteness of swans
a herd of swans
an eyrar of swans
a gargle of swans
At a rough guess there were at least 200 swans feeding and today's blip can only record part of the "bank, bevy, whiteness, herd, eyrar or gargle" of swans. They seemed to be having a real feast.