sing like a canary

sing like a canary

To inform against someone to the police or other authority about his or her criminal or illicit behavior. I heard Joey Malone has been singing like a canary in the hopes of getting his sentence reduced. Let's make sure he's sleeping with the fishes before he gets the chance!
See also: canary, like, sing
References in periodicals archive ?
Tell them you wanna talk and, hopefully, they'll follow your lead and sing like a canary.