RavensGryf is 100% correct.
The first two pictures are females.
The last two pictures are males.
As you have mixed genders, please be absolutely sure you do everything necessary to discourage breeding if the four budgies are housed in the same cage.
Rearranging their cage frequently, and limiting the light they get to 8 hours a day will help tremendously. Please be sure you never put a nest box or anything that could be used as a nesting site in their cage.
When they come into condition, limit the amount of protein in their diet at that time.
Thank you! although my dad, is coming next Friday and he's going to put them together. I have told him not to because of the employees at PetsMart said " The younger birds felt threatened by the older birds. You can't ever put them together again." Should I? They used to bully Chiketa. Please help!
You can’t always believe everything a big box pet store employee tells you. They are often uneducated about birds, and usually aren’t bird owners themselves.
The age has nothing to do with it. Regardless of age, any newcomer to the cage will be met with at the minimum a little pushing around until pecking order is clear. It’s best to rearrange the cage; major branches, eating areas, toys, etc. so that territoriality may be reduced.