I have had two birds most of my bird life..I had Smokey for about a year,then Amy came along..Amy was 16 weeks old and Smokes was about 1.5 yrs old. They lived in separate cages but across the room from each other,always in sight and hearing. Smokey was a jealous girl..if I had Amy with me in the kitchen,playing on the table or whatever,Smokes would waddle down the hallway looking. Smokey NEVER came down the hall on her own! Only if Amy was with me!
And if they were out of their houses,Smokes would walk up to Amy,wait till Amys back was turned,then yoink on her tail then run away!
Once many years ago,they went beak to beak,where Smokey bit Amys tongue,requiring 5 stitches

After that, I made sure they didn't get too close to each other.
When Smokey passed away this April,before I adopted Jonesy..I could tell Amy was grieving. She was very quiet and would not come out of her house.
Now,with Jonesy,Amy is back to laughing and talking and she wants to be friends with Jones,but he is a very cunning little so and so..acting real interested in Amy,then clunking her on her head with his beak!
So...2 birds or 1?? lol..I was looking for a second after Smokey passed..I'm happy with the outcome, I just pay extra attention when both are out.
Jim