If the parts are intact to make noise after a head impact I would assume its possible for the animal to make noise just as the body and wings/ legs thrash about from the brain being shut down. I have heard many animals make noise after a clean solid brain hit but its usually a noise that resembles more of a moan from what sounds like the air left in the lungs being pushed out from muscle spasms. I have had several starlings scream when hit but they were all from heart lung shots.
I've had it happen with ground squirrels.
I've had squirrels cry out after a clean headshot! No zombie dance or crazy twitching, just a loud cry out and then silence.. Has to be the nerve endings just seizing up at the moment of impact.[/quote+1
I never really thought about the physiology of a headshot. But it's really kind of messy business there's no such thing as a clean headshot
You might want to check local game laws I believe Grackles and Mocking Birds are protected species