About the Andean cock of the rock, Wikipedia states “The nests are often constructed from the saliva of the females mixed in with vegetable matter and mud.”

“often”

This means that nests could also be otherwise constructed. Maybe sometimes it’s not mud. Glue could work well. Maybe sometimes it’s not vegetable matter. They’re on record as occasionally eating reptiles, so maybe sometimes it’s meat. Maybe they just super glue a bunch of snakes together and lay their eggs in that.

So many possibilities.