Ataxia may be defined as an inability to coordinate the voluntary movement of muscles. Birds that are ataxic appear wobbly or clumsy and will often stand with the legs spread far apart in order to balance or hook their beak on the side of the cage. When severely ataxic, they will stumble and fall from the perch. If ataxia is the result of nervous system disorders, other symptoms, such as trembling, head tilt, circling, star-gazing or seizures, may also occur.

Ataxia may occur due to disorders of the nervous system or musculoskeletal system. Nervous system disorders often result in an inability of the brain to perceive the position of the limbs, body or head in space or an inability of the brain to coordinate movement. This may occur as a result of damage to the spinal cord, inner ear or brain. The spinal cord carries information to the brain about the relative position or placement of the body, wings, head and legs. The fibers that carry this information are located on the surface of spinal cord, so relatively mild damage to the cord will cause ataxia.

Ataxia is usually one of the first symptoms of spinal cord or nerve damage. Birds with damage to peripheral nerves or the spinal cord usually have symptoms localized to the affected appendages and the level of mental activity is normal.

The inner ear and portions of the brain (medulla and myelencephalon) are responsible for maintaining balance and a normal body position. Damage (from infections, trauma or pressure) to the middle ear or brain will cause severe ataxia. Usually, these birds have other neurologic symptoms, such as a head tilt, circling, abnormal mental activity or seizures.

Metabolic disorders, such as diseases of the liver, kidneys, pancreas or parathyroid glands, may also affect the brain. Birds with metabolic disorders may not be able to eliminate toxic metabolites, or may be unable to regulate blood concentrations of glucose or calcium.

Birds with musculoskeletal damage may also appear uncoordinated, as the muscles are unable to respond properly to signals from the brain. This may occur with deficiencies of nutrients such as calcium, vitamin E or selenium or electrolyte disorders. Birds that are extremely weak from chronic diseases also appear ataxic. Ataxia is always a sign of serious disease warranting veterinary attention.