New moult pattern in diurnal raptors: primary moult pattern of the Japanese Sparrowhawk Accipiter gularis

Abstract

ABSTRACT In the family Accipitridae, the primary feathers (p) are moulted sequentially from p1 (innermost primary) outwards to p10. In comparison, the primaries are moulted divergently in the family Falconidae, starting from p4 (and sometimes p5), and simultaneously ascending towards p1 and descending towards p10. This moulting process is considered to be representative across diurnal raptors. Here, the moult pattern of the Japanese Sparrowhawk Accipiter gularis was examined from museum specimens and from direct observations of live birds. Two types of moult patterns were detected, with 13.2% of birds exhibiting a ‘normal-type’ moult and 59.4% of birds exhibiting a ‘new-type’ moult, while patterns could not be detected in the remaining 27.4%. During the non-breeding season, the primary feathers generally moulted outwards in the normal-type moult, starting from p1 and ending at mostly p8. In contrast, the intensity of the new-type moult varied among individuals, with most individuals moulting feathers between p4 and p8 and replacing their primaries between p3 and p10.