We've all heard of pecking order in birds. It's a designation of hierarchy indicating who has the greatest power in the flock. You can usually pick out the highest ranking bird when observing the activities in a cage full of birds. The highest ranking bird is allowed access to the bath first. Other birds move away from the food dish when Top Bird approaches. This lower ranking bird behavior is not like the fawning deference sycophants give to an emperor, but rather a practical matter of letting someone be alpha to keep things nice and peaceful. Let Top Bird use the swing and he won't peck your head. It's a no-brainer for the average bird with no aspirations toward leadership.
There are other interesting social activities happening in a birdcage. For instance, you can tell who is friends with who, by what you might call Perching Order.
Birds that are pals sit close to each other.
Then there are the times when even good pals don't want to be joined at the hip.
Then there are birds who are not pals. For such birds, an Allow at Least Two Bird Lengths Between Cage Mates rule applies.
Some cage mates would rather not share the same perch.
This is why it's a good idea to offer plenty of perches in a cage, this increases the likelihood that each bird will have as much space as is desirable. Giving the caged bird freedom to maintain his personal space keeps squabbling at a minimum.