Blackbirds, crows or ravens?

[LuvOrlando]

So I live in the Lehigh Valley PA and now that fall is rolling around we have more black birds floating around. But, some have yellow beaks and some have black beaks while some seem enormous compared to others. Are these all the same birds at different ages, hence the size differences with different beak colors or are they actually different birds?

Does anyone out there know because this has been bugging me for years and I don't have clue?