In the wild, budgerigars breed at the times of year when food is most plentiful. However, in captivity, they can nest at any time. According to The Complete Book of Budgerigars breeding time for captive budgies in the tropics occurs from April to October, while breeders in temperate climates prefer June to December. Your budgies will probably have their own schedule, but you can control when breeding occurs by providing materials for nesting at the appropriate time.
An obvious sign that your budgies are ready to breed is their flirting behavior. Budgies that are ready to mate will spend lots of time "chatting" with each other, touching beaks and grooming each other. The male usually makes the first moves, approaching the female and showing off by fluttering his wings or making noise. Give a flirting pair of budgies plenty of light and lots of healthy food -- it's important for both male and female to be at the peak of health when breeding commences.
Female budgerigars do most of the work when it comes to breeding, including making the nest and incubating the eggs. An obvious sign of readiness to mate in a female is nesting behavior. A female budgie may chew up newspaper, books or other soft things to make her nest. If you've provided her with a nesting box, she'll spend time inside preparing it for eggs. Her cere, the soft part of her nose above her beak, will turn brown, according to Budgie-Care.com. She may also start regurgitating food, as if she were feeding chicks.
Male budgerigars make it very evident when they're ready to breed. They engage in lots of flirtatious behavior and not just with female budgies. Male budgies that are ready to breed may flirt with anything. The cere of a male budgerigar should turn bright blue when he's ready to breed. You may also see him feeding the female regurgitated food, as if she were already incubating their eggs.