Gyaos appeared on Himegami island.
Many people were killed and eaten.

The "birds" then flew to the Japanese
mainland and preyed on many people.

The Japanese Self Defense Force was
in the process of capturing some Gyaos
for study when Gamera interfered.

Gyaos can grow to have a
wing span of 180 meters.
They also can emit "sonic beams"
which can destroy metal.