There is no known same sex aggression between bird species. If you do not wish for your birds to breed, then purchase two birds of the same sex to keep together. You may wish to purchase a small cage to move one of the birds to during mating season as an alternative to purchasing two or more of the same sex.
Younger parakeets are often a better purchase than those that are more mature. Young parakeets are easier to hand train and are easier to teach to talk. It is possible to tell a young parakeet by the black bars that cross the feathers on its forehead. A parakeet with clear yellow or white forehead feathers is close to or at physical maturity.
Well-socialized chinchillas often make wonderful pets, particularly if they are hand tamed by the breeder. As with any animal, it is better to purchase your chinchilla from a breeder, rather than from a pet store. Some chinchilla clubs provide literature to pet shops free of charge, so that their shoppers can know how to care for their new pets.
