Track of a bird (4)
I believe the answer is:
rail
I believe this is a double definition.
'track' is the first definition.
(I know that track can be written as rail)
'a bird' is the second definition.
(a wading bird)
'of' acts as a link.
(Other definitions for rail that I've seen before include "Bar; waterbird" , "Rant" , "Bar for hanging; bird as corncrake" , "Complain about - marsh bird" , "Scold, berate" .)