What specific feature of the terror bird's skull anatomy was optimized for powerful strikes without excessive weight?

Answer

Hollow interior reinforced by thin-walled trabeculae

Fossil evidence from a small subspecies suggested the internal structure of the beak was hollow and reinforced by thin-walled trabeculae, optimizing it for impact without excessive weight.

What specific feature of the terror bird's skull anatomy was optimized for powerful strikes without excessive weight?
birdPredatorextinctfossilterror bird