What finer materials are used primarily to line the inner cup of the Scissor-tailed Flycatcher's nest?

Answer

Hair, rootlets, and plant down

The inner cup, which is smaller and deeper than the outer shell, is lined meticulously with finer materials like hair, rootlets, and plant down.

What finer materials are used primarily to line the inner cup of the Scissor-tailed Flycatcher's nest?
birdornithologywildlifeScissortail