Wild ravens will still spore a tame raven. Just supply many nest boxes and wait for some wild ones to come by. Any hatchlings will be tame, because the mother is. It just depends on if your biome supports giant ravens, then it's only a matter of waiting for a flock murder to pass by...
Hate to be that guy (again), but this one's important.
A murder is crows, a group of ravens is collectively referred to as an "unkindness".
Ravens are crows. An unkindness of ravens is also a murder of crows. That's 'cause the Crow is the Family Corvidae while the Raven is the Species. For a moment of heartwarming, Magpies (also from the family of Crows) are Tidings. So it's comes from the Unkindness of the Ravens to upset the Crow family, leading to a murder of Crows. Since it's a family, the kind Magpies come with tidings. Neat thing I just thought.
Google magic, my friend.
EDIT: Adendum: Brazillian portuguese doesn't have a word distinguishing Crows from Ravens (they're all Crows, or Corvos). We have a word for Magpie (Pega-Rabuda), and they're all from the family Corvidae. Also, there's no such thing as "Murder of Crows". All groups of birds are flocks. Little culture for you folks!
Whoa, whoa, whoa, whoa, whoa!!!
True, but ... not quite correct! While both crows and ravens are in the same family, the Corvidae, as are magpies, that doesn't make them the same thing. Both crows and ravens are genus
Corvus, but almost everything that's named "Raven" is more closely related, evolutionarily, to other things named "Raven" than to the things named "Crow". Ravens tend to be bigger with proportionately heavier bills. So, we English speakers have taken the words to distinguish between the two types, even if other speakers have not.
And while flock may work for "any bird", it's not like the English didn't say "murder of crows". The phrase may be archaic, but it does exist.