Armor for a Bird? Any rules or book with info?

[Knaight]

I just want to add that, having worked with falcons, hawks, and eagles in the real world, the idea of "barding" a bird is a non-starter. We make backpacks and foot attachments for small electronics payloads, but these things weigh grams.

You could probably get away with armoring an ostritch or emu, but that really just demonstrates your point.