Keep finches and small birds in aviaries. While any type of bird can be placed in an aviary, probably the most popular are finches. Finch aviaries are inexpensive to create, take up little space, and provide a fascinating glimpse into the lives of these small creatures.
Aviaries can come in all sizes.
One of the easiest forms an aviary takes is a cockatiel hotel cage. These cages, usually with dimensions of about 17W x 17L x 36h, make nice beginning aviaries. I would not recommend a cage smaller than this because aviary birds stay in their enclosure all their lives. We must remember, that although finches are small, they still require room to fly. There are no set rules for the number of birds to place in an aviary.