Unless you live on a farm in the middle of Nebraska and the nearest house is thirty miles down the road, birds do not become dependent on you as a sole source of food.
Birds come to feeders for supplemental food.
They prefer to eat natural food, and given the choice between ant steak and sunflower potatoes, a chickadee will go for the steak.
But they can be enticed to a feeder for the pleasure of the watcher, and the watcher should always remember that he is not feeding birds for altruistic reasons.
Therefore, the feeder should be kept clean.
If you go on vacation, take the feeder down, both for sanitary reasons and because birds can get their heads caught trying to get the last few seeds from some feeders.
If the feeder is missing, the birds will quickly go elsewhere for snacks, but once it is put back up, the birds will be back in a week.