None of this applies to crows. They're very happy to eat our rotting corpses and day old vomit. So feeding them can be an adventure if you try hard enough.
I tried that once. I fed a bunch of crows some walnuts while sitting by a river, and it was fine. The next day I came back, I fed crows at the same spot, and soon a murder of other crows came and attacked the crows I just fed. Not even just lightly nabbing them, but hacking down on them continuously until I broke up the fight. Didn't try feeding any since then.
Sidenote: because of the weird position of my feeder, only one bird can eat at-a-time. House Sparrows being smart and loving do the following.. one goes to my feeder and shoves/throws down seeds, so he/she eats straight from the feeder, and a bunch of others eat the seeds falling on the sidewalk.