Outside of the breeding season, canaries should always be kept apart.
Male canaries fight with each other, sometimes with fatal results.
He might also kill the female, if she is not ready to breed. Several canaries may be kept, in separate cages, in the same room. This sort of arrangement will encourage the males to sing, but is not necessary for the bird's health or well being. When not breeding, it is not always easy to tell the male canary from the female. Only the male sings and only the female will build a nest.