What is a one-sentence summary of the following article?
Males are known for being much noisier than female budgies. They will chirp or sing and the songs can be quite long. While female budgies make sounds too, they usually sound angry and less musical. However females can be just as cheerful just as males may be grouchy.  Keep in mind that behavior should not be solely taken into consideration when determining sex. Both sexes can display the same behavior. Male budgies frequently bob their heads up and down or tap their beaks against their cage. They'll appear playful and outgoing. Female budgies may seem more aggressive if they're in the mood to breed, subdued, or if they're fertile. You may notice a male budgie tap against a female and regurgitate food to her. Don't worry. This is normal bonding behavior and will occur between same-sex pairs, too. When you buy your budgie from the breeder or dealer, ask the budgie's sex, though be aware not all breeders are informed, especially if colony breeding. You can also purchase inexpensive DNA kits that also reveal the budgie's sex. Don't forget that you can ask your veterinarian to determine the sex of the budgie. This will be easier if the vet is familiar with treating birds.

Summary:
Listen to your budgie. Watch your budgie's behavior. Ask someone knowledgeable.