Bird - mine scratching pole - muffles a quack (6)

I believe the answer is:

magpie

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'bird' is the definition.
(magpie is a kind of bird)

I don't understand the rest of the clue.

(Other definitions for magpie that I've seen before include "Chatterbox" , "Black and white bird - a thief" , "Half of 1D [GAME OR BIRD]" , "said to bring sorrow" , "chatterer" .)

I've seen this clue in the Sydney Morning Herald.

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