It's easy to distinguish between male and female canaries, because only males can sing. The singing capacity of the male canary is heightened during the breeding season, when it tries to court the female. The male canary also demonstrates several other traits that signal it is ready to mate.
Canaries are photosensitive and breed during springtime. As winter ends and spring approaches, the males are ready to mate weeks earlier than the females. A male canary may display restlessness and harass the female by aimlessly chasing her around the cage. In certain cases, the male can turn aggressive and kill the female if she is not ready to breed. Therefore, male and female canaries should be housed separately until they are both ready to breed, and only when the female has built her nest.
Male canaries can get quite romantic during the mating season. If the male is in the same cage as the female that it is interested in courting, he will feed the female and even kiss her. If the canaries are kept apart, the male produces romantic, visual signs --- such as by feeding and kissing the corners of his feet or any V-shaped niche in his cage. The couple is ready to mate when the female accepts food and acknowledges the display of affection from the male.
Canaries are excellent singers, and a sexually mature canary male will sing more than normal to attract the female. He accompanies his lustful singing by rocking back and forth on his perch and gradually moving closer to the female. If the female is ready to mate, she may respond to the male by chirping or assuming the mating position.