Hello fellow newbie, Hef here. I'm sure some of the old timers here will correct me if I'm mistaken, but Bird Engineering is different than Fox Corp/Sprite. If your bike has an engine plate shaped like a pentagon (5 sides), it's a Fox. Square/rectangular would be someone else possibly Bird, who made bikes for Sears, Wards, Penny's etc.
I'm not able to post links etc but if you google image search for Fox Corp minibikes you'll find some good stuff. Same for Bird.
Good luck!