Zebra finches and cockatiels can be housed together, but care must be taken to ensure one bird is not dominant or aggressive toward the other. It's usually best to house birds of similar sizes together, but the zebra finch and the cockatiel are both gentle varieties so they can get along, depending on their personalities. Birds of the same gender do better together, especially if you plan to keep them in the same cage.
Larger birds tend to dominate smaller birds. This can happen with a cockatiel and zebra finch. The larger cockatiel may dominate or bother the tiny finch. If you're housing the birds together and find this is the case, separate them. Bird varieties of similar sizes usually do best when kept in cages or aviaries together.
Cockatiels are passive, friendly birds and usually won't pick a fight unless they feel their territory is being invaded. If you add a zebra finch to your cockatiel's cage, he may pick on the smaller bird. If you had the cockatiel first, he might be jealous of a new addition. Introduce your cockatiel to other birds at as young an age as possible. Cockatiels tend to be more accepting as youngsters. Cockatiels get along with most varieties of parrots, who are similar in size.
Zebra finches get along well with other varieties of finches and also do well with some larger birds. Finches can be aggressive if they feel threatened by larger birds and become territorial during breeding season. This is not a good time to introduce another bird. They do well when housed with canaries, who are slightly larger than finches but not as large as a cockatiel.
Introduce your zebra finch and cockatiel slowly and carefully. Keep them in separate cages initially, in the same room. Gradually move the cages closer together until they are next to each other and the birds can become accustomed to one another without invading the other bird's space. Watch for signs of angry squawking or aggressive behavior -- a sign that the two birds will not get along.
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