That large, raven-like bill serves the currawong in many ways - currawongs are consumate predators of lizards, birds' eggs and nestlings and large insects, but are equally at home consuming fruit or seeds.
Any resemblence to a raven is superficial or convergent; currawongs are in the essentially Australasian family Artamidae which includes butcherbirds, Australian magpies and woodswallows.