If you don't know whether your new budgie is a boy or a girl, look at the cere, the waxy-looking area above the beak, surrounding the nostrils. Cere color reveals the gender, but you can be misled if your budgie is immature and you don't know the color code.
If your feathered friend is under 4 months old, it will be difficult to determine the sex. At this stage, both sexes have purplish-pink ceres. Occasionally, you will find one with a pale blue tint. With closer observation, you may be able to get a hint of the sex. If you notice that the cere has a more translucent quality to it, it's likely a young male. If the cere has a more chalky quality, this will indicate a young lady. After the bird's first molt, you will be able to distinguish the sexes with increased confidence as the coloring becomes more distinct.
The adult male budgie normally sports a royal blue cere. If the male budgie's cere isn't a very bright blue, it will turn bright blue during mating season. Outside of breeding season, the adult female budgie's cere will be tan, beige, light brown, white, or white with a hint of pale blue. During breeding season, her cere will take on a dark brown color.
There are exceptions to the color coding rule. If the adult male budgie is albino, lutino (yellow with pink or red eyes), dark-eyed, clear or recessive pied, he may retain his youthful purplish-pink cere throughout his life. It's something to remember when you are determining the sex of your budgie.
Although the cere is usually smooth with a waxy appearance, at times this will not be the case. When your adult female is “in season,” her cere will look more wrinkled and crusty. If your feathered friend's cere doesn’t have its normal smooth appearance, it may indicate he's getting sick. A trip to the vet is in order.