My budgie's nose changed color. How do I tell its gender?

Thank you for the additional pictures! I see what you mean about the purple coloration around the top of the cere (around the nostrils). Just below the nostrils, there looks to be a darker rim - as mentioned before, this looks like it may be starting to turn brown. Typically when we see male budgies start to turn colors, that it is more of a true blue color initially and not as much of a purple color. Based on this, I still think that Snowflake is mostly likely female. Thanks again for the additional photos!

Budgies are born with blue Ceres. As they age the females Ceres with fade to a yellow brown color. Based on your description, it sounds like Diego may be a female. I recommend using a nesting box that you can pick up from your pet store. It may take some time before Diego gets used to using it.

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.

It looks like Ruby is pretty young, and it is hard to determine sex in young birds. If the cere is turning pink, brown, or crusty, Ruby could actually be a female that is becoming sexually mature. If the cere becomes very deep blue, that is usually the sign of a mature/active male. However- in some color variations cere color doesn't always indicate sex correctly. If the brown is separate from the cere, is discharge, or you're seeing any signs of illness, then this could indicate an issue such as a respiratory infection which should be checked out by your vet.

Bruno appears to be female. This is determined by the color of her cere ("nose"). In female budgies, it is flesh colored, in males it is noticeably blue. She may be coming into her breeding season which could be a potential cause for the appearance of her cere. She would have to be physically examined by your veterinarian or a vet experienced in treating birds in order to diagnose any infection in the area.

Poor Violet! Some crusting around the nose and a sudden cere color change can indicate the possibility of an infection going on, especially if there is discolored discharge or crusting stuck to the nose. Cleaning the nose and removing any debris may make things more comfortable for Violet, however if it returns or she begins to show signs of illness, having a vet take a look is best. They may need to flush the nostrils of any debris, or start Violet on an antibiotic or fungal medication to resolve the issue.

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/