In my version of the False Knight - AKA outlandish knight the bird is promised a cage of beaten gold and a perch of the best ivory

I do not have a version of Henry Lee.

A perch of ivory would fit the same space as the various sugestions though, and it would not be beyond credulity for it to have been misheard and resulted in 'no need for poverty' and the like.

I just realised recently that I had written down 'one more line' for the line in the song in 'due south', rather than 'one warm line'as I didn't hear that when writing it down. All part of the folk process.

Anne