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. During the Summer and early Fall, it takes a well informed canary fancier to detect the gender of a bird hatched that year. When shopping for a hen, go to a store that will guarantee the bird - allow a replacement if the wrong gender is supplied.
Canary hens are generally in good supply from mid-summer until early autumn.
With nesting finished for the year, fanciers sell off their excess birds. They are not easy to obtain at other times of the year. Plan to purchase the female at the earliest opportunity. This will give the bird a chance to adjust to her new home. Very rarely are productive hens sold during the breeding season.