Warm areas then unknown for migrating bird (4,10)

I believe the answer is:

manx shearwater

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'bird' is the definition.
(Manx shearwater is an example)

I can't explain the remainder of the clue.

(Other definitions for manx shearwater that I've seen before include "Bird" , "Dark-backed seabird, Puffinus puffinus" , "European seabird" .)

I've seen this clue in The Times.

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