The first thing to consider is the size of the cage. You want your pet bird to have sufficient room for both food and play. While a cage for a finch or canary can be smaller than one for a parrot or cockatoo, you should always seek a "roomy" home for your feathered friend. Bigger is better. Cages that are too small can cause your bird to scream, bite, pluck feathers and and other nervous behavior.
A bird cage should have the bars spaced so that the animal will not get trapped between them. For small birds like budgie, lovebirds and even cockatiels, bar spacing of one-half inch is best. Larger birds can have up to one inch spacing, depending upon how large the bird's body is. Ask your vet or pet shop what is recommended for your species.
The shape and style of cage for your pet bird should fit both the bird's needs and yours. Round cages are poor choices except for finches and canaries. All other birds prefer square or rectangular cages. Decide if you want to place the cage on a cage stand or if you want one that can be hung. Big cages, of course, aren't for hanging and usually have a stand or, if extremely large, sit directly on the floor and extend most of the way to the ceiling.
Choose a bird cage that is constructed of sturdy material. Thin bars on a cage for a large bird will result in broken bars as the bird chews on them. Choose a powder coated finish to prevent rust.
By following these tips, you should find an adequate cage that will keep both pet bird and owner happy.