Birds sound like doves with empty tummies (5)

'birds' is the definition.
(coot is a kind of bird)

'sound like doves with empty tummies' is the wordplay.
'sound like doves' becomes 'coo' (I can't explain this - if you can you should give a lot more credence to this answer).
'with' is a charade indicator (letters next to each other).
'empty' says to hollow out the word (remove centre letters).
'tummies' with its middle removed is 'ts'.
'coo'+'ts'='COOTS'