How did the Greeks do special effects of vultures in the play Prometheus Bound?

In the ancient Greek play "Prometheus Bound," special effects for the vultures that torment Prometheus were likely achieved through the use of stagecraft and clever staging rather than actual animals. The Greeks employed masks and costumes to represent the vultures, possibly using actors who mimicked the birds' movements and sounds. Additionally, the theatrical conventions of the time allowed for symbolic representations, so the audience would understand the presence of the vultures as part of the larger narrative without needing realistic depictions.