Unfortunately you are trying to create an entirely unnatural situation. You need to better understand bird behavior to realize that the three birds simply can’t be caged together and expected to be “friends”. To begin with, it’s never a good idea to keep an odd number of birds in one cage, regardless of what sex they are. Birds are social, but they don’t really have friends – not in the way we have friends. Dogs and cats can be companions, and you can have more than one of each, but these are a domesticated animal that was bred to be this way. Your finches may be captive bred, but they are still wild species, with wild instincts. It’s true that the society finch is considered to be a domesticated species, since they were bred by humans from other species and do not exist in the wild. But the Spice finch is a wild species and is never going to be social in the way society finches can be. Finches will form a mate bond with another finch, even a different species and even if they are the same sex. Once they have this bond, other birds are seen as rivals, and will be driven away or killed. Pip considers Baebae to be his mate. He defends him by attacking Cheerio. If you continue to try to force them to get along, Pip will end up killing Cheerio, or Cheerio may finally fight back and kill Pip. The chasing was a warning, the loss of feathers was the fighting getting serious. The next time you are going to lose a bird. A finch can pin down a rival and kill it in a matter of minutes! I can’t stress enough that you have to stop trying to mix these birds. The reason Baebae is fine with Cheerio when they are in Cheerio’s cage, is that this is Cheerio’s territory. When they are in Pip’s cage, Baebae is acting the way he does because he knows that Cheerio is invading Pip’s territory, and both Cheerio and Baebae are at risk of being attacked. Pip is the dominant mate in this case, and if he can’t drive Cheerio away or kill him, he is very likely to turn on Baebae and start attacking him. This is because if they were a wild pair, the female would be driven back to the nest or back away from the rival. Since they are in a cage, Baebae can only get so far, and Pip is going to turn his aggression on Baebae if he can’t overpower Cheerio. Presumably they do not have nests – they should not have nests because only breeding birds need a nest, and only during breeding season. You can’t keep moving Baebae to Cheerio’s cage. This is very stressful to Pip and just isn’t fair to him. And at some point, he may get mad when Baebae is returned to their cage and attack Baebae. You need to either get a female for Pip, and let Baebae & Cheerio live together, or get a companion for Cheerio. But given Pip’s aggression, do not ever try to put all four birds together.
I also want to warn you not to ever let the lovebird be in contact with the finches, because a lovebird will maim or kill a finch. They have a strong, hooked bill and the finch can’t defend itself against a lovebird or any parrot species. Your lovebird is your companion, and does not need to be around the finches. It’s OK to have several birds, and different species, but understand that there are behaviors and instincts to consider, so mixing birds as far as letting them have contact with each other, can be tricky and often is not possible.
Thank you for asking Lafeber,