What prominent physical features on the Eurasian Eagle-Owl's head are explicitly stated to be feathers, not actual ears?

Answer

Prominent ear tufts

The bird is instantly recognizable by its prominent ear tufts, which are noted to be feathers and not actual ears.

What prominent physical features on the Eurasian Eagle-Owl's head are explicitly stated to be feathers, not actual ears?
birdfaunaNorth Americaowleagle-owl