You get the same reaction if you blow a duck call. We live along the Chattahoochee River, and the Canadas and mallards are heading back north - when they fly over honking and quacking, Shelley goes nuts. She dances on her hind legs and leaps in the air and barks . . .
Lu isn't bothered by the Canadas that live in the area year round. They fly over at rooftop height and honking away. She looks up like they are annoying. Probably because she hasn't dealt with real birds on retrieving.