I've thought about it before and just this year put out a can of the hair I take from my brushes for nests. It disappeared rapidly. Since I have neither cut nor trimmed my hair nor beard in a number of years there is quite a lot of it, most of it gray... uh, white.
Perhaps the strangest nests I've seen were some dove nests at the refinery I retired from on the Houston Ship Channel. The main material of construction was small pieces of stainless steel tie wire the insulators had nipped.