My parents have an African Grey parrot Benny and his intelligence is simply amazing. First, he can talk sentences and he mimics my mom pretty good. Second, he can connect sentences to meaning, so for example, when I enter the room he'll greet me, when I leave the room he'll say goodbye. If he's hungry he'll also tell you that (actually, he is hungry most of the time :)) And I think that crows have a similar intelligence level like African Greys, so their potential is really huge.