Why did my mother parakeets kill one of her female adult offspring?

Question
QUESTION: Since 2005 I have had 5 parakeets, 3 females, two males. One is the mother; the father died in 2005. They got along except of an occasional fight until 3 weeks ago when I saw the mother (Sunni) attacking one of females named Patience. I removed the mother from the cage for two weeks. I put her back in the cage and monitored the mother with the other bird and everything seemed fine until I came home last week and saw the mother and Patience at the bottom of the cage and Patience head was half gone. Sunni had pecked her to death. Why would she do this?

ANSWER: Dear Deidre,
thank you for your question.
It's very rare for parakeets to actually kill another member of the flock. They may fight for several reasons, for example for a male, for a nesting box or because the attacked bird is sick or dying. I think that Patience may have been ill, a healthy bird would fight back and I don't think that Sunni could have killed her unless she was already weak. Parakeets hide illnesses very well so that predators and other members of their flock don't notice, so you might never have seen any signs of Patience being sick.
This may sound brutal, but it's instinctive behaviour, a sick bird would draw predators to the flock and so it's better to chase it away. Since that's not possible in captivity, the sick bird may get attacked again and again until it's dead.
I'm sorry this happened to you and I hope I was of some help to you
Jennifer

---------- FOLLOW-UP ----------

QUESTION: Is it safe for Sunni to go back in the cage with the rest of her flock? She acts like she wants to go back and the other birds want her back, especially Cutie. Cutie loved Patience and misses her. She's in the cage with her brother Sweety, but they are ignoring each other. I was hoping they would bond. Should I move Sunni to another room? Do you think that would help Cutie and Sweety to bond?  

Answer
I think that it's at least worth a try to reintroduce Sunni to the rest of the flock. If possible, do it during the weekend or whenever you have time to watch them for a day or two to make sure that they don't fight (some pecking to re-establish the order is normal).
Parakeets don't accept any bird as a partner, so Cutie and Sweety may not bond regardless of whether they are kept as a pair or in a bigger flock. If they like each other, they will bond even if the flock is huge.
I hope I was of some help to you
Jennifer