The American Araucana chicken produces blue eggshells, which is a unique trait of this breed, which is an autosomal dominant inheritance trait. If the Araucana is cross bred with any other breed of chicken, its offspring will lay greenish-blue colored eggs. On occasion they can produce alternate, rare egg colors such as pink or yellow colored eggs. Araucanas unfortunately carry a "lethal gene", so that breeding two tufted birds together results in 50% with tufts, 25% of the brood dying in the shell, and 25% having no tufts.
The breed has no tail (referred to as being rumpless) and so-called ear tufts, which are feather-covered epidermal appendages that project from the side of the chicken’s head. The tufts are associated with an irregular external ear opening and a reduced external auditory canal.