A great range of different colors, has been produced in budgerigars by breeding in captivity. The cere, which is the rectangular, fleshy area above the upper mandible (bill), varies in color with the bird's sex: the male's is a rich blue or flesh color, and the female's is chocolate brown. In the very young female the cere is pale watery blue.
There are four digits, two pointing forwards and two pointing backwards, as in all members of the parrot family. Normal body temperature is 42.2 deg. C. Adult weight is about 50 grams.
The young are blind and naked when hatched. Eyes open at six days and at one month the plumage is complete. Adult budgerigars moult irregularly throughout the year. However, control of. light and dark and control of humidity can regulate moulting. There is no way of estimating age accurately, except by leg rings. Older birds tend to have longer upper beaks and their nails grow longer with age and become more friable. In immature birds the plumage markings are fainter, and the forehead shows faint, dark bars. Sexual maturity is reached at three to four months, but cocks should not be used for breeding under ten months, and hens under eleven months. The lifespan varies - females up to six years, males up to eight years, though some birds live to twenty years.
Budgerigars are hardy and can be kept outside all year round once they are acclimatized.
As pets they benefit from daily exercise and can be allowed to fly around the room or around the house, although care must be taken with glass windows and mirrors.
Budgerigars will breed all year round if allowed. If possible have equal numbers of the sexes and pair them in separate cages before introducing them to the breeding aviary. Some pairs are incompatible.
Compatible birds rub their beaks and 'kiss' and the cock feeds the hen. If the hen declines the cock she pecks him and refuses to be fed by him. The nest box should be introduced some five to seven days after mating a pair. Most hens commence to lay at ten days after nest introduction. If they do not, they should be returned to the aviary and another hen substituted. Because eggs are laid every second day, the young hatch every second day. They are born bare of all feathers.
Budgerigars live in flocks naturally and hence may be kept in community cages. Breeding will take place in wooden nest boxes 15 X 15 X 23
centimeters. The entrance hole in each box should be 4 centimeters in diameter, with a perch provided in front of the entrance. Breeding boxes should be left uncleaned, as the excreta provides a good source of heat during its decomposition. Perches should be 12-17
millimeters in diameter, and the birds will also relish irregular twigs for perching.