The tits, chickadees, and titmice constitute the Paridae, a large family of small passerine birds which occur mainly in the Northern Hemisphere and Africa. Most were formerly classified in the genus Parus. These birds are mainly small, stocky, woodland species with short, stout bills. Some have crests. They range in length from 10 to 22 cm. They are adaptable birds, with a mixed diet including seeds and insects. Many species live around human habitation and come readily to bird feeders for nuts or seed, and learn to take other foods.