male zebra finch tail feather loss

Question
QUESTION: I have one male and one female zebra finch. they padded their nest and are mating and sleep side by side in the nest. They preen each other and seem to get along. What I cant understand is why the male is missing most of his tail feathers. I found the feathers in the nest. Can you give me some advice on what i should do?????

ANSWER: Sounds like they're using feathers as nesting material. This is easier remedied. Just buy them more nesting material. Obviously they want something softer. The website provided has soft nesting material that my birds absolutely love.

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QUESTION: I use cotton balls.Whats softer than that? could it be an illness?

Answer
Cotton balls aren't exactly the easiest thing for them to work with. I find that my birds also like Timothy Hay (found in pet stores) and sisal fiber (the website provided)-they get really creative with the sisal.
I highly doubt it's an illness. Worst case scenario is that either himself or his mate is pulling out his tail feathers.