How to tell a budgie's age by its cap, cere, eyes, or leg band?

Your budgie is probably somewhere between 6 and 12 months of age. The head is free of "barring" which is present in younger birds. The eyes are not clearly seen in the images provided. Look for iris rings. Older birds have a well developed iris ring. Younger birds have none or very faint iris rings. If the rings are faint in Polie's eyes, she is likely closer the 6 month end of the estimate.

If they are at least 12 months of age, you can determine gender by looking at the color of the cere (nose). In males, the cere is a blue color. In females, it is tan/brown. If they are younger, you will need to wait or you can have them sexed by DNA using blood or feather samples.

The color of the cere (the area just above the beak) is essential to understand the gender but unfortunately before 8months old is very difficult to visually distinguish males and females. Please repost your question in few months so we can help you assessing sex. Generally speaking I would recommend to have a look at this website for anything concerning your budgies. http://www.beautyofbirds.com/

Penny looks like a female. If she has a closed band on one of her legs, her hatch date and the breeder's initials may be imprinted on it. If not, it can be very difficult to determine age. You can get an approximate age by looking at her eyes. If they are completely black, she is 4 months of age or younger, if there is a faint ring in her iris then she is between 6-8 months. A distinct white iris ring puts her at 8 months or older. Clipping wings, when done properly, is safe and does not hurt the bird. Only the primary feather should be clipped. If you have never clipped wings, allow your veterinarian or an experienced avian vet to clip them first. Clipped wings are replaced with new ones when a bird molts.

A closed band indicates a captive bred bird. An open band indicates a wild caught or imported bird. Unfortunately, there is no universal system for reading leg band information. The first three letters may be the breeder's initials. The "17" may indicate the year of birth, clutch number or chick number. The last letter may indicate gender.

The band is an identification band. The numbers and letter may indicate the year hatched, the breeder, place/state of origin, and chick number. It should not be removed. Kiki will likely not "outgrow" the band. It is small enough to not slip off but big enough to not be restrictive.

A male albino budgie will have a flesh colored cere instead of the bluish colored cere. Females will have a brown cere. If it is perching and moving in the cage normally, I wouldn't worry. A young bird may not have the gripping strength that a mature bird may possess. However, any new bird should be examined by your veterinarian or a vet experienced in treating birds.