The owl is a bird of prey, noted for its stealthy night-time activity. Classically, it was the archetype of wisdom; to medieval Christian moralists, it symbolized the Jews. It’s a period charge, dating from c.1295 in the arms of Seyvile [ANA2 205].
The owl is usually depicted with “ears”, tufts of feathers on either side of the head, to distinguish it from other birds. Its default posture is guardant close, as in the illustration; but even when in other postures such as rising, the owl is guardant unless specified otherwise.
James MacChluarain bears: Sable, an owl argent.
Flann Ua Cuill bears: Or, an owl gules.
Morwenna de Bonnay bears: Purpure, three owls Or.