Ardea
Official journal of the Netherlands Ornithologists' Union

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van der Weyden W.J. (1975) Scops and screech owls: vocal evidence for a basic subdivision in the genus Otus (Strigidae). ARDEA 63 (1-2): 65-77
Among the owls Otus is by far the genus richest in species, comprising about 40 out of a total of about 130 species. A taxonomic revision of this highly complicated genus has recently been undertaken by Hekstra (in prep.). In connection with this revision, a survey is presented of territorial songs of 30-odd Otus species, based on tape-recordings, and on descriptions in the literature. The song of nearly all species studied appears to be a monotonous repetition of mostly short and often pure notes. Using tempo, pitch and number of notes per motif as the main distinguishing characters, a simple classification of the songs is possible. From a vocal standpoint, the genus can largely be divided into an Old World and a New World group of species. However, the North American Otus flammeolus appears to be closer to the Old World species, whereas the African O. leucotis shows vocal affinities with the New World group. The classification thus obtained largely parallels Hekstra's subdivision of the genus Otus into Scops Owls and Screech Owls. Although there are a few species with a somewhat intermediate song, no such species is likely to constitute a link between the two groups. It is argued that a division between Old World and a New World group is not surprising for a genus of mainly (sub) tropical distribution. It appears that O. leucotis, O. albogularis, O. nudipes and O. podarginus, which have been excluded from Otus by some authors, fit well, as regards there songs, in the genus. Thus, song seems a useful taxonomic character, not only at the level of the (super) species, but even of subgenus and genus. Geographic song variation was found in all those widely distributed Otus species where sufficient material was available for judgment.


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