Birds making tracks? (5)
I believe the answer is:
rails
I believe this clue is a double definition.
'birds' is the first definition.
(rail is a kind of bird)
'tracks?' is the second definition.
('rail' can be a synonym of 'track')
'making' is the link.
(Other definitions for rails that I've seen before include "secretive birds" , "For trains" , "Makes a protest" , "Water birds" , "Barriers of horizontal bars and supports" .)