The majority of crows mate for life. Although they reach sexual maturity at age two, many crows don't mate until later - they are waiting for the right partner. Unless their partner is killed, most crows stay with the same mate, year after year.
Leave no black plume as a token of that lie thy soul has spoken! Leave my loneliness unbroken! --quit the bust above my door! Take thy beak from out my heart, and take thy form from off my door!" Quoth the Raven, "Nevermore.