Those eyes on the grackle make it very easy to distinguish a grackle from a crow! I feel pretty good about distinguishing a raven from a crow, too, as long as I am close enough to eyeball its size! Crows are so gorgeous, and I'm not just saying that because they are in my last name! :D
1. I would say that, actually, it's probably a chipmunk or squirrel killing the baby birds.
2. I live in the city so any walk I take I'm likely to see 5-10 crows on it!
3. I do live where there are both species. I have seen a raven only once that I know of, at a bird sanctuary. They are enormous! So much bigger than a crow. It is easier to tell the difference between them up close.
4. Since crows keep insect and rodent population down, humans really benefit from crows! Crows also benefit everyone by spreading seeds and berries, so any animal who relies on seeds and berries would benefit.
BONUS: I love to see crows and when I get up close to them you can really see them as mini raptors.