There are several explanations for this loss of feathers. First, this total feather loss may be a normal occurrence for individual birds during their post-breeding molt. The loss may also be caused by mites – in this case skin mites. The mites are perfectly natural (and not caused by diet) and relatively harmless, unless the bird is in an otherwise-weakened state. The mites exist on the birds in the only place the birds cannot preen themselves-on the head. They should have a new set of head feathers in a month or so.
Some authorities also believe the simultaneous loss of head feathers may be due to factors other than or in addition to mites, such as nutritional deficiencies, high temperature, or other environmental stress.
It would be best to report this to local health officials so the birds can be observed.
