Categories: Behaviour / neurological phene

Mendelian trait/disorder: unknown

Disease-related: yes

Clinical features: Conner (1953) " the defect under study was never observed before the birds were 25 days old, and usually did not appear until they were two or three months of age. ... The birds were normal in appearance when undisturbed except for a forward arching of the neck. When disturbed, the affected birds draw the head completely below the body and shake the head rapidly from side to side. This posture was usually maintained for some time, although often the birds fell backwards, apparently due to a loss of balance. ... Death was usually due to an inability to eat and drink."

Pathology: Conner (1953) "Autopsies have shown that no internal lesions, such as those of Newcastle disease, leucosis, or nutritional deficiencies, were present in affected birds. No gross lesions of the central nervous system have been found."