Australia declared "war" on them in 1932, in an attempt to stop them from destroying crops (4)

I believe the answer is:

emus

(Other definitions for emus that I've seen before include "Fast, but not high-fliers" , "laboratory units" , "Muse about flightless Australian birds" , "Largest native Australian birds" , "Aussie birds" .)

I've seen this clue in The New York Times.

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