French Moult

French Moult is a peculiar virus disease infecting budgerigars under three weeks of age. It appears that the virus, Polyomavirus, by itself is relatively harmless and the apparent random nature of French Moult in the breeding cages is explained more by the immune response of the individual birds to the virus rather than the virus being particularly nasty.

French Moult causes the loss of primary feathers (wing and tail) while the young are still in the nest box. Many recover and go on to regrow their lost feathers.