Feather duster budgerigars (Melopsittacus undulatus), sometimes called budgerigar mops, are budgerigars that have a condition characterised by overly long feathers that do not stop growing at usual periods, giving the bird the appearance of a feather duster.
The shaft (calamus) is also curved, and so the feathers appear deformed and fluffed out.
Individuals with this condition often appear less alert than nest mates.
They lack vigour, often cannot fly and die within a year of hatching.
There is no treatment for the condition; birds are often euthanized in the nest.