Q: Can a male cockatiel and a female budgie live in the same cage?
Linda S. Rubin explains:
That depends upon several factors, such as their individual personalities, how you introduce them but most especially, diet. I recommend keeping each bird in its own separate cage at first. Then allow the birds to explore each other’s cage of their own accord, say, while out for exercise.
Or, you can introduce the birds in neutral territory, such as on an open playpen or activity center, in a large flight, or cage, where they can escape if one bird should become aggressive or territorial.
Only allow birds to share one cage if you know they truly desire to be together. Never place birds together in a cage without closely monitoring their behavior — for at least several days — or force birds to live together where one, or both, become aggressive over feed cups, water cups, perches, mates (even a mirror image), or other perceived territory.
Since your birds are different species, a problem does exist in your situation. Cockatiels eat a different diet than budgies. Although a cockatiel mix contains the same seeds as budgies, it also contains some safflower, sunflower and other high-fat seeds. Safflower contains some lipids, and a lipid by any other name is still fat and not appropriate for a budgie.
While budgies and cockatiels can be trained to eat pelleted or extruded diets, and both enjoy the same fresh, leafy greens, fruits and vegetables, it is considered risky to place a cockatiel on an all-pellet diet. Some studies suggest that, unlike other members of the parrot family, cockatiels fed a 100-percent pellet diet can possibly develop kidney damage. However, this can easily be avoided by simply adding seeds and vegetables to their menu of pellets.
If you simply must house your budgie and cockatiel together, you could offer both budgie-size pellets (which are made smaller than cockatiel size) and cockatiel-size pellets, along with a standard budgie mix and fresh produce. It is possible that your cockatiel might steal the budgie size pellets, so be sure your budgie is eating them. (Although, keep in mind that it is usually the smaller budgie that intimidates the more gentle cockatiel and behaves more territorially over food!)
If you choose to follow this menu, you could offer your cockatiel its larger seeds separately each day, in very limited amounts due to their high-fat content. Never allow your budgie access to sunflower or safflower seeds, which are not part of its diet. Both varieties are highly fattening, and budgies are prone to developing fatty tumors and liver disease.