Vocal repertoire of the Japanese brown hawk owl Ninox scutulata japonica

"The vocal repertoire of the Japanese Brown Hawk Owl Ninox scutulata japonica was studied based upon the detailed observation of behaviour and sound recordings of wild birds with additional data of captive birds. In adult birds, there were at least thirteen types of vocalizations, K-HOO (the song), HOH, GUF, OO-COO, POO, HYU, KRRR, CHEE, MEW, MEEEW, HOOH, QUAY and BUF, with a possible addition of BYAHBYAH. Also, there were three non-vocal sounds: wing clapping, wing rustling and bill snapping PACK. The development of vocal repertoire was studied during the first year of life. Nestlings had 4 vocal sounds of LEEE, GILILILI, CHILILILI and KYRRKYRR, and a non-vocal PACK. Fledglings increased the number to the following 8 vocal sounds: LEEE, GILILILI, CHEWLEE, BYAHBYAH, PUH, SOO, POOH and O-GUF. Juveniles further added PY-O, BEH, SCHEEE and PUR. The subsong O-GUF O-GUF appeared after 10 weeks, and some of juvenile calls transformed to adult versions afterwards. The physical structure of sounds was analysed by sonagraph. Their behavioural contexts were surveyed for both sender and receivers before, during and after sound production. Based upon the results, messages and meanings of sounds were interpreted for further discussion of functions after Smith (1977a). In particular, K-HOO was discussed for its relevance as the song. In the adult repertoire, K-HOO, HOH, GUF, OO-COO, POO and HYU were graded in the physical structure. Their relationships were closely examined for both physical and behavioural aspects, which showed a good correspondence. The development of vocal repertoire and underlying motivational mechanism were further examined. Motivation-structural model by Morton (1977) well fits in the graded vocalizations. Comparison was made between Japanese birds and other races or congeneric species to draw the minimal design of Ninox vocal repertoire: the song, shrieking, screaming, a cat-like mewing and trilling. Further, 87 species from 21 genera of the Strigiformes were reviewed. Twenty-seven species out of them had more than 5 types of vocalizations, and the maximum number of adult repertoire was 14 vocal sounds and 3 non-vocal noises. Juveniles had 1-4 vocalizations and 1 non vocal sound. Japanese birds reached the largest repertoire. General accounts of the species are compiled to cover the description, classification, distribution, habitat, general behaviour, feeding, hunting, breeding, the pair-bond, nest and territory, based upon the original observation in 1974-1981 and the past literature including those published in Japanese"--P.1.