Why do birds chatter?

I like to watch chatty birds, I like to watch how they move and dance about with each other, but mostly I love the constant chatter. I want to know what they are talking about, what they say to each other and why it matters. But as a scientist, I also wonder why? Why all the chatter? Do they exchange “gossip” on other birds. Do they say, Missus so and so had an argument with her sister, now they are not exchanging tips on where the best food is?

Why talk, why communicate? Well, communication allows for the exchange of information, where the best food is, where everyone else is heading, when everyone else is ready to fly away, as well as anything else that matters to a bird. You would expect this to be of great importance in birds that live together in a group- communication is paramount.

With the apostlebirds that I study, they chat and chat and chat. Constantly. Lots of calls. Calls while looking for food, calls while preening, calls before flying away, calls when they approach me, calls when they sit on nest, calls when they switch nest duties, calls when they leave the nest, calls when they are scared, calls when they are alone, calls when moving newly fledged birds, calls when they approach a rival group, calls looking at me. They never shut up. What are they saying? Does this smooth out their social interactions?

Here's a little video clip of the birds in a calmer setting (so no initial excitement of food).