Wouldn't the intelligence level of any animal be relative to what you are comparing it to? They have survived until now same as we have. By assigning a "level of intelligence" to any animal, are you not humanizing them yourself? Just by saying it is a smart or dumb bird you are assigning human values to it.
As far as whether they are just dumb birds goes, what are you using as a measure? They know which bugs to eat and which to stay away from and which plants are better than others, I couldn’t tell you that... They instinctively know to build a nest in a dark protected area to lay there eggs in. They know to take care of there young and protect them. (That is the ones that haven't been breed by people to not be broody)They know to roost as high as they can to not get eaten at night. They have survived this long and that is more than you can say for millions of other species, and in my humble opinion that takes a degree of intelligence.
They do have documented vocal patterns used to warn others of danger or food or to scare predators or establish dominance, so just because they don’t write poetry is not to say they don’t "talk" in there own way. Along with vocal patterns they also use body language and posturing as people do.
They do show primal emotions, you can defiantly tell when they are scared or content or angry. They have a desire to be in large numbers and watch out for each other as people do. As with people are some that are mean, some that are nice, and some that are just weird/goofy and some that are affectionate just as people are. I have had all sorts of them over the years.
I guess my point is that intelligence is relative. Kev you are right chickens are not people but that doesn’t mean they are just dumb birds either. They can’t do many things people can do, but on the other hand can you fly, or lay an egg, or sleep standing on a tree branch, or have taken care of yourself at only one day old?