Domestic chickens are artificially bred to grow large breasts, and the extra weight from this muscle tissue makes it difficult for chickens to fly. Domestic chickens are also trained to stay near the roost and not to fly off, which breeds against developing advanced flying abilities.
The domestic chicken descends from the Red Junglefowl. In the wild, Red Junglefowl forage for food on the ground but roost in trees. These wild fowl are capable of both running and flying reasonably well.Learn more about Chickens