Loud bird is cockerel perhaps (4)
I believe the answer is:
fowl
'cockerel perhaps' is the definition.
(I know that cockerel is a type of Gallus gallus)
'loud bird' is the wordplay.
'loud' becomes 'f' (short for forte - 'loud' in music).
'bird' becomes 'owl' (owl is a kind of bird).
'f'+'owl'='FOWL'
'is' is the link.
(Other definitions for fowl that I've seen before include "eg Chicken" , "Bird kept for eggs and meat" , "Bird, maybe domestic" , "eg hen" , "Domesticated bird" .)