Hi Aussiechick
According to my 'Oracle' in this case "A Dictionary of English Surnames" by P H Reaney & R M Wilson
Bird, Birds, Byrd, Byrde is Old English, a nickname 'bridd or 'bird'
Sometimes, no doubt, metonymic for birdclever, or Bird Catcher.
It goes back to 1193 - William Brid
As far as crests go:
Byrde in Kent, Byrde in Lincs, and
Byrde generally - On a Dolphin, embowed, ppr, an eagle, wings addorsed, or
Chris in 1066Land