Poultry are a great source of eggs, meat, pest control and entertainment. They compliment other animals, as they will scratch around in their manure, eliminating maggots, and clean up the larger animals' scraps.
Chickens are probably the first animal that people will get going on their homestead, mostly for their eggs. They also produce meat and help with pest control. However, you need to provide them with a safe haven as predators will seek them out.