sexing budgies
Sex can normally be determined at four months old by observing the ceres colour.The cere of young males is normally pinkish/purplish blue while the adult is bright blue.Young females have blueish white ceres,changing to brown when adults.Some females retain a light blue tinge that may crust and turn brown during the breeding season.
I hope the pictures of these varieties will help you overcome any difficulty when sexing your birds.
Hens in breeding condition showing a nut brown cere
Hens out of breeding condition and showing the white/blue cere
Adult cocks coming out of a moult and into breeding condition
Imature cocks showing a purple cere
Mature cocks in breeding condition