Bittern evidently eating another bird (4)

I believe the answer is:

erne

I'm a little stuck... Click here to teach me more about this clue!

'another bird' is the definition.
'erne' can be an answer for 'bird' (erne is a kind of bird). I am not certain of the 'another' bit.

'bittern evidently eating' is the wordplay.
'eating' indicates the answer is hidden within the clue.
'ERNE' can be found hidden inside 'bittern evidently'.

Can you help me to learn more?

(Other definitions for erne that I've seen before include "River and lake of the North" , "Eagle, river and lough" , "Sea eagle and Northern loch" , "White-tailed eagle" , "European sea eagle" .)

I've seen this clue in The Telegraph.

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