Budgie Communication is classic Bimbo Yoohoo
No, really, budgies chirp chirp chirp, but it seemingly never changes. This implies there are sounds modulated onto that chirp we cannot hear, or that repetitive chirp actually has variety, only it is so subtle or fast we cannot distinguish a change. If they talk, I don't hear it.
Budgies do have a rather rich body language. Probably the first one you will spot is face-knawing. It looks like they are kissing, but there seems to be an element of intimidation too. Fighting males will also bite at the face, but they also pull feathers, sit on the opponent, push him up and down a perch. Wherever the poor thing wants to sit, is never good enough for the bully. The fighting is always about

breeding rights, and in an overpopulated cage that means a serious battle of budgies every time a hen wants to lay an egg, because clearing a nest of some other bird's eggs or young takes a bit of violence. We don't like violence, budgies don't like violence and besides, it cuts down on that incessant chirping if they stay happy. Happy budgies still chirp away, but it sounds less strident. Aha! There is a difference in modulation after all. The things we don't know we know...
Cold budgies tend to cuddle up to themselves, all fluffy they crawl into themselves on their perch. A budgie trying to climb into himself on the floor, is a sure sign of something being wrong. Even if it's just hiding from a bully, leaving it there will not help it. A temprorary warm spot sometimes helps to revive them. Usually, we put down a large quantity of intersting food. That keeps the bullies occupied long enough for the scared one to warm up and have something energising and revitalising to eat. That usually does the trick for us, though we have much to learn yet. I blame our habitat arrangement for that; the budgies are not in an ideal environment, and it was designed to show off bird ownership, instead of bird husbandry, one of the reasons we tamed ourselves some engineers and suchlike, to design and build things that work. We also have people who stand around afterwards and critique the way it looks.
That's how we keep track of public opinion for the price of one or two beers. First you demolish their inhibitions, for friends are obliged to lie supportively. You also irritate them slightly, so they feel critical of you. People can really tear into your ego after a few. Their critisism, if warranted and constructively useful, gets incorporated into the next generation of habitat or device or methodology. Some of our things we sell with a lifetime warranty. It is not that we trust our materials so well, those are the things we don't trust to stay good long enough for the intended use, and closing a deal like that with us means you get your machine or tool, and we will replace/repair/upgrade it for free for as long as we agree the thing was poorly made or designed. This way you have the latest model for free for as long as can be expected, and we get a guinae pig to test our stuff in real life conditions. I don't understand too much of that, find the engineers advertising somewhere on our pages, they have the oddest ideas on saving money on technology. Something about Entry-Level Retrofitting or somesuch. Anyway, we will post pictures of the new habitat soon, see you then. In the meantime, go read up on the the interesting things we feed our budgies. By the time you come back from the harvest, we should be done.