Veerafwijkingen bij nestjonge Haviken Accipiter gentilis veroorzaakt door ‘Franse rui’?

In previous issues of De Takkeling two cases of feather anomalies in a nestling Goshawk from the same nest in different years were described. A review of the literature shows that the defects are most likely caused by French moult, affecting growing flight feathers and causing them to break off. Unlike in “pinching off”, thus affected birds are unable to form new feathers, even after completion of a full moult cycle.