OK the longish answer:
I have 8 caiques. Average age 6.
1) My partner kept a lovebug Quaker called Noodles. Beloved Noodles was a close to human as a bird could be, and a total sweetie. He grew up with the caiques. Ate with them. Played with them every day.
Until one day they tried to beat him to death. So badly they beat him, that his bones were visible in many places. They seriously wanted him dead. Luckily he survived and was moved far away from them.
2) I sold most of my lovebirds after two unexplained deaths in the avairy they shared with the caiques.
3) 2 of my green thighed caiques cannot stand the sight of the yellow thighed variety. They launch screaming flying attacks at any and every opportunity. I have been bitten separating them. They are so enraged they don't recognize me.
4) Fingers and Cha Cha, 8 years old and paired for years have taken to fighting. They cannot be left alone. They scream at each other in long piercing shrieks of annoyance. Violence is next.
5) NUM NUMS, a one year old hand raised baby, will fight any birdie for food, no matter how much food is strewn about everywhere. She is HUGE. The Hulk of the bird world, and she throws her weight around. She is afraid of nothing.
6) Gorgeous little baby Nick Nak plays wrestling with my hand every evening. She lies on her back in my lap and wrestles my fingers with feet and beak. She loves it, pretending to be outraged by my touch and resisting energetically.
If I get distracted and stop wrestling, she will nip my hand hard to get my attention and restart the play fight.
Why is nature preparing her to fight like this?
What would she do to a weaker bird?
These birds are strong wrestlers with a high energy lifestyle. They love fighting. For play and for real.
No other species is safe around them.