They should also be able to make short flights. Horizontal bars on the sides of the cage are very important for birds that like to climb, such as parakeets, cockatiels and lots of playful parrots. Bar spacing needs to be small enough that the bird cannot get it' s head through them. Metal bars are good for birds that like to chew. It is really nice if the cage is easy to clean.
Many cages have a slide out tray and an easily removable grate.
The cage should be placed in a draft free area that is well lit, but not in direct sunlight. To make your birds feel secure and comfortable keep their cage against a wall or in a corner, and at eye level if you hang it from the ceiling. Aviaries are beneficial in providing large areas for birds, often with the intent of breeding. Aviaries can be either indoors or outdoors. Some birds are very noisy and can be a nuisance to close neighbors.