Age determination of Brown Hawk-Owl (Ninox scutulata)

Abstract

Age determination of Brown Hawk-Owl Ninox scutulata was carried out based on the following: mistnet-captured owls in Tochigi and Niigata Prefecture, central Japan; the images of specimens in Yamashina Institute for Ornithology; and images found in books and websites. The juveniles have tapered rectrices with a broad pale fringe that is as wide as the inner pale bands. The adults, however, have broad, rounded rectrices with a narrow whitish fringe. The juveniles molt body feathers without fright-feathers and rectrices in autumn; therefore, the rectrices are useful in age determination until complete molt the following summer.