Why would a mother parakeet kill another grown female parakeet that shes been caged with for years?

Okay so you said a "mother" parakeet, well if you don't know when it comes to animals and their children you don't mess around with them. The parents are very protective of their children. Maybe that other bird went near the other birds babies and the mother got mad. Or maybe they got into a fight. But she's been caged with her for years? Hmm this is puzzling. Well im like really sure about the whole baby reason. Wait by any chance did you have a male bird??? If so maybe they were fighting over that mate? Or over extra space in the cage??? Sorry for your loss Sincerely. echub The only recorded instances of parakeets fighting is in captivity. It is very rare, and always it is among females. There are two reasons they fight. They would fight over a mate, or fight over nest space. Fighting over nest space is the most common, but is still rare. You need twice as many identical nests as you have female parakeets. That means if you have two parakeets you need 4 identical nests. You can remove the extra nests only after each female parakeet has chosen her own nest, and really you should leave an extra nest or all the extra nests as a precaution. Also you cannot house two female parakeets and one male. That doesn't work. You need to house a male and a female, or two males, or even three males and one female. If you need to house two females together, you must make sure there are more males than females. That means if there are two females you need three males. =End New Answer= A mother parakeet would do that because she would probably want to protect her babies. Try buying a male. The mother budgie shouldn't kill this one. Hope this helps you.