Could be taken for auks (though perhaps not by an ornithologist) (4)
I believe the answer is:
skua
'perhaps not by an ornithologist' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'could be taken for auks' is the wordplay.
'auks' can be anagrammed to 'SKUA'.
But, I am not clear how this is indicated.
'though' is the link.
Can you help me to learn more?
(Other definitions for skua that I've seen before include "Auks (anag.)" , "One preying on gulls" , "Large predatory bird" , "Seabird; sounds like pin" , "Flyer" .)