I see and hear this over and over again, and I have not the slightest idea where it comes from.
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According to 'Brewer's Dictionary of Phrase and Fable', from Ecclesiastes x. 20:
The first thing that came to my mind were Odin's ravens, Thought and Memory who "brought information to Odin".
On Wiktionary, they make reference to the same Bible phrase AND a connection to Norse mythology.
From The Phrase Finder
Phrase Finder says that the root source of this expression probably is biblical, from Ecclesiastes; see Barrie England's answer, above.
(The phrase "feathered or otherwise" seems odd. I thought all birds, by definition, had feathers.)