They don't eat them. They ruin them. They taste them. They peck them.
They mutilate them... but they don't eat them.

If they ate the berries they would get full and have to stop.

As I now take all the the pecked berries and lay them next to the
birdbath -- where they are ignored -- I would like to know if there
are any other good ideas on how to discourage them?

This seems to mostly be robins eating the blackberries. I think some
people use netting but it seems that that would be a mess to handle.
How about something that would vigorously wave a flag and chime every
few minutes? I may have to build something.