Why is the crow black?

I was taking my post lunch walk today when a crow flew-by. At this point one of my friends would have started calculating its speed, but it occurred to me that I don't know why is it black. After all it hunts in the day so its color is not an aid for hunting (as it would be for hunting in night). Or maybe crows got their color in some other region and migrated here. But then probably they would discolor over time. But never the one to prefer thinking over googling, after coming back I put the question in the search box. Here are three answers I found, you are free to take your pick.

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