Abstract
The Jungle Nightjar Caprimulgus indicus is found from India eastwards through southeast and eastern Asia. A subspecies, the Japanese Jungle Nightjar C. i. jotaka, migrates in summer to the Japanese islands of Hokkaido, Honshu, Shikoku and Kyushu. Although sexing of this species has long been available, detailed information on aging had not been described. In an earlier paper, the author reported on molt and aging in autumn. This paper provides data on molt and aging in spring. The research was implemented at Watarase Marsh, Tochigi Prefecture, central Honshu in May, 2003. One male was captured and observed on May 17th. The data from this bird was compared with photographs and specimens obtained from other Japanese banding and recovery records. A total of six individuals were utilized for comparison. The results show that both adults and juveniles have a mixture of old and new feathers in spring. This indicated that they begin molting on their wintering area, but do not complete the molt until arriving in the breeding area. Both adults and juveniles have old (non-molted) feathers in their greater primary coverts. In Juveniles, however, these old feathers show a light-colored edging, which is absent in the adult (Fig. 1, left and Fig. 2, left). Both adults and juveniles also retain old tail feathers. Adults, however, tend toretain inner feathers, while juveniles retain outer feathers (Fig. 3). In addition, the old feathers of juveniles are thin and rounded, while those of adults are thick and angular (Fig. 1, right and Fig. 2, right). Based on data from this research and prior research conducted in autumn, a tentative schedule of molting can be reconstructed (Fig. 4). Juveniles begin molting into 1st winter plumage in the breeding area. During their first winter, they molt partially into adult plumage, but still retain some juvenile feathers when they arrive back in the breeding area.
