This is a good example of how a group of birds drive fish ahead, in this case into the banks of a rice field.
These Pelican swim forward grabbing the fish as they move.
The fish keep ahead of the birds until they run out of water or against a shore.
A friend was photographing large flocks of Egrets using the same technique. They were so efficient the fish jumped out of the water onto the banks all around where she was hiding in the reeds. Large flocks become an eating machine.
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These flocks will move on when the fish are gone. The fish return with the tides and water flows between the marshes.