The chicken is the world’s most numerous domesticated bird, with over 52 billion farmed worldwide in 2008, rivaling the dog as the most ubiquitous domestic animal globally. These birds have fascinated scholars and researchers since the dawn of Western civilization, and recent studies are beginning to reveal the depths of their complexity and cognitive ability. According to Andrew F. Fraser, professor of veterinary surgery at Memorial University of Newfoundland, and Donald M. Broom, professor of animal welfare at University of Cambridge: “Those who have studied the behaviour of the domestic fowl in detail…, especially those who have looked at feral fowl…, inevitably acquire much respect for the members of this species.”
The Humane Society of the United States, "About Chickens" (2010). Farm Animals, Agribusiness, and Food Production. Paper 5.