Psittacine Beak & Feather Disease in wild Sulphur-crested Cockatoos is caused by a virus transmitted by inhalation, or direct contact with infected surfaces. PBFD is found mainly in parrots and cockatoos, but all psittacine species may be susceptible to infection. It destroys the feather follicle, causing deformation of new growing feathers. Ultimately the follicle is destroyed, feathers are unable to form, and as the bird cannot fly death is inevitable in the wild. The beak may be deformed, as in both of these birds where it is laminated and elongated due to incorrect growth, and feeding is inhibited. These two wild birds, at a bird feeder, appear to recognise each other's predicament and huddle up close for friendship. (Though anthropomorphic, close observation over many weeks led to this conclusion. ) // Sulphur-crested Cockatoo - Psittacidae: Cacatua galerita; Length to 65cm, wingspan to 105cm; widely distributed in northern and eastern Australian woodlands, urban and suburban areas , New Guinea west to Indonesia (uncommon). May be a pest species in grain-growing areas.