If you've ever seen birds at a pet store, you've probably heard them talking to each other. Budgies, which are often kept in groups, are almost constantly chirping to each other. But most birds will talk to each other if there is more than one in a cage. This is normal flock behavior, in essence the chatter is a vocal reminder of who belongs to the group, and where they are. Sometimes when Peanut is on my shoulder (or on my head, or on the neck of my turtleneck), he and I make "kissy" noises to each other. It's pretty amazing to be considered part of a bird's flock.