Moult patterns in the Long-tailed Hawk Urotriorchis macrourus

Abstract

Information is presented on moult of the Long-tailed Hawk Urotriorchis macrourus, based on 51 specimens. The postjuvenile primary moult is descendant, but the annual primary moult is descendant in about half of the cases only and regular serial descendant moult was found in a few, but different asymmetrical patterns occur in other specimens, probably in relation to accidental replacements, physiological stress or consecutive breeding attempts. As in some other raptors, the brown juvenile central pair of rectrices is replaced by the piebald new generation of feathers before the body and primary moults. These feathers probably signal the individual's status as a potential breeder. As in several other very long-tailed birds, annual rectrix replacement is a permanent ongoing process, which is largely asymmetrical, particularly in the central two pairs, resulting in one feather having always a new contrasting aspect, which may help in signalling status.

Ostrich 2007, 78(3): 577–582