The first type of pet that you might consider keeping as well as your parakeet would be another type of bird. Other than parakeets together, these guys are actually very, very docile birds. You can keep them with other small Australian birds including Australian finches, as well as cockatiels. These guys actually co-habitat in the wild, so you can generally keep them together without any problems. You do need to be careful when introducing the birds since they are different species, and you need to make sure that you have an extra large cage if you were keeping these birds together as the cockatiels are much larger than the budgies are. But generally there aren’t any problems.
So basically if you’re going to do more than one species of bird in the same cage, you need to have a much bigger cage so that they can fly away from each other. Both birds need to be flighted so that they can get away if they need to and you need to observe them for the first few days to make sure that there isn’t going to be any conflict. I don’t recommend, at all, mixing these with any American or South American species of parrots or anything else other than finches or cockatiels. They’re not used to each other. They’re not native together in the wild, so you definitely want to make sure that you, if you are going to use other birds in the same cage that you stick to those particular species.
Other pets, it doesn’t matter how friendly you think your dog or cat might be, you need to be very, very careful. All it would take is a very small swipe of the claw on a cat to kill these birds. The cat doesn’t even have to bite down. If the cat near swipes at these birds and gets a nail embedded in their skin, cats nails have so much bacteria on them from the cat’s licking their feet, that these little birds will get septicemia, which is a blood borne bacteria, and just die. They’ll seem fine two days later, three days later you’ll find them dead at the bottom of their cage. They do not do very well at all. Dogs, even if your dog doesn’t seem predatory, a twenty five pound dog that bumps into these birds or steps on them can either break them or kill them, so you need to be very, very careful.
Basically, other than just other native species with these birds, these guys really don’t get along with any and it’s not to say that your budgie won’t be okay with there being a dog or cat in the house, it’s just that the dog or the cat might not be good for the budgie, so you need to be very careful when both introducing these species and always have both under observation unless either your parakeet is in a safe cage in a location that your cat or dog cannot reach, in which case you could probably leave the room. Otherwise, they always need to be supervised together. I just can’t think of any other species, obviously fish, but you’re not going to put them together, so. Use common sense.
Remember again the size of these of these birds. You can have other birds in your household of different species, but you just need to keep them in separate cages. If they’re not either, again, finches or cockatiels, just, again, be careful. The larger parrots, even if they’re not caged together, if they’re both out playing together at the same time, if this bird flies and lands on the other bird’s cage, that bird might get territorial and bite a leg off. I’ve seen it happen, so you have to be very, very careful with these small birds. They have a very big personality and once they feel very comfortable in a household, there’s almost nothing that scares them and they will stand up to an animal twice their size, ten times their size, without a whole lot of fear, which is very dangerous for them. So it’s your job to protect them when they’re out of their cage.