Like most birds, parakeets love shiny objects. A faceted bead, sparkly piece of glass or metal ring can provide hours of entertainment. For most parakeets, mirrors fall into the category of an enticing sparkling object. But they also offer something more interesting, the image of a bird reflected back at your parakeet. This can be a good thing for some parakeets and a bad thing for others.
Isolation
Parakeets are highly social; they can become depressed if left alone too long. Even an afternoon spent in isolation can upset a parakeet. A mirror will help some parakeets feel like they have a friend in the cage. This can help cheer up a lonely bird. Parakeets can spend hours looking at, preening with and chattering to their reflection. For some birds, this can have a long-lasting positive effect.
Obsession
For some birds, a mirror in the cage can turn from a joy to an obsession. A parakeet may start preferring the company of the mirror to that of his human. He may refuse to leave his cage or move out of the line of sight to the mirror. Some male birds will even start regurgitating on the mirror, as if offering up a meal to a mate. This can result in excessive weight loss and be dangerous to his health. If your parakeet is obsessed with the mirror, remove it entirely, or leave it in the cage only when you are going to be away for several hours at a time and remove it again when you return.
Aggression
Instead of becoming obsessed with the reflection, some parakeets will become aggressive toward it. Unable to understand the image is not actually another bird in the cage, a parakeet might feel like his space has been invaded. He might attack the mirror or become agitated without attacking. On the other hand, parakeets truly obsessed with a reflection can become aggressive toward any other bird or human that attempts to get near the mirror. Permanently remove the mirror in cases of aggression.
Safety
Even if your parakeet has a positive response to the mirror, safety must be a priority. Mirrors designed for parakeet cages are meant to be unbreakable; however, check for weak or broken plastic pieces that could give your bird unwanted access to the edges or back of the mirror. Regular glass mirrors not designed for birds may contain chemicals in the backing that can harm your parakeet if he ingests them. Provide your parakeet with mirrors designed for birds to avoid injuries. Check the mirrors periodically for wear and for secure attachment to the cage.