Can you feed crows corn or bird seeds?

Yes you can. Crows are actually scavenger birds, which means they will eat whatever they get their hands (wings? beaks?) on. Including roadkill.

They are known for hijacking bird feeders and stealing corn from farm fields (they're smart, eventually they'll figure out that the scarecrow is fake).

But it is not advised that you purposefully feed wild crows. Wild crows are sometimes seen as a pest because they will unroot plants to get at the seeds or bulbs, hijack bird feeders, scare off or fight off the friendlier birds such as Songbirds and have sometimes been observed attacking cats (oh and they'll also eat a dead cat). Crows display very similar behaviour to vultures. Be careful when feeding them as to not attract too many to the neighbourhood.