Family TYTONIDAE

Tyto (Megastrix) novaehollandiae

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Family TYTONIDAE

Compiler and date details

R. Schodde & I.J. Mason, CSIRO Australian National Wildlife Collection, Canberra, Australia

Introduction

Tytonidae (barn or masked owls) comprise about 10 to 17 species in two genera if bay owls (Phodilus Geoffroy Saint-Hilaire, 1830) are included; five species in one genus occur in Australia. The Australian fossil record of extant species of Tyto Billberg, 1828 is limited to the Holocene-Pleistocene, from southern Western Australia to New South Wales and the Cooper Creek basin, South Australia. The family is almost cosmopolitan, with its centre of diversity from South-East Asia to Australia.

Tytonid owls are nocturnal or sometimes crepuscular predators that, usually solitary, roost by day with head erect in tree hollows, holes, under ledges or under tussocks, and hunt on the wing at night to catch small vertebrates (commonly rodents) in their talons, carrying them in either feet or beak, and swallowing them whole or in large dismembered pieces at perch, regurgitating the indigestible parts in large, smooth pellets bound with vitreous mucus. Nests are unconstructed beds in hollows, holes or tunnels under tussock swards; eggs are ellipsoidal, plain dull white, and are incubated by the female; young are altricial, nidicolous and moult quickly through two successive downs (protoptile, mesoptile) to fledge in near-adult plumage.

Family-group Systematics

Tytonidae Mathews, 1912 are treated here as a family distinct from the hawk owls, Strigidae Leach, 1820, after Sharpe (1875), Beddard (1888), Peters (1940), Wetmore (1960), Mees (1964), van der Weyden & Ginn in Burton (1973), Condon (1975), Clarke et al. (1978), Schodde & Mason (1981), Sibley et al. (1988) and Sibley & Monroe (1990)—and for reasons given under the latter family, cf. Amadon & Bull (1988). Tytonidae comprise two genera—cosmopolitan Tyto Billberg, 1828 and palaeotropic Phodilus Geoffroy Saint-Hilaire, 1830—which are so different that they are placed by convention in separate subfamilies, see Peters (loc. cit.), Wolters (1975–1982), Cramp (1985), cf. Marshall (1966) who recognised Phodilidae Beddard, 1898 as a family. Traits separating Tytoninae and Phodilinae are summarized by Milne-Edwards (1878), Beddard (1890), Pycraft (1903a), Verheyen (1956) and Miller (1965).

Note: prior to about 1910, Strigidae was used as the name for this family because Strix Linnaeus, 1758, the basionym for Strigidae Leach, 1820, had been misapplied to the tytonid owls (Mathews 1910).

Genus-group Systematics

Tyto Billberg, 1828—Although Tyto Billberg, 1828 is widely accepted as a well-defined genus, relationships among its component species-groups are still poorly understood cf. Schodde & Mason (1981: 61) and White & Bruce (1986). Diversity is greatest in the region of Australia-Papuasia-Sulawesi where 11 allo- or semi-specific forms occur, most of them with apparent affinity to the masked owl group, treated here as subgenus Megastix Kaup, 1848. Given that tytonid owls form an old divergent lineage among Strigiformes, it may well be found that, upon deeper investigation, their component species-groups warrant generic separation and that the subgenera accepted here are polyphyletic.

Species-group Systematics

Tyto alba (Scopoli, 1769)—Tyto alba (Scopoli, 1769) sensu lato, the world's Barn Owls, comprises four or five major regional forms, of which Australasian delicatula Gould, 1837 is one. It differs from other forms in its pearl-grey rather than warm tawny dorsum and, according to J. Pettigrew (pers. comm.), in its visual accuity which in turn affects its hunting behaviour. It may be allospecifically distinct from alba Scopoli, 1769 sensu stricto, but interactions with other forms cannot be tested under natural conditions at present, those stocks introduced with American T. a. pratincola (Bonaparte, 1838) to Lord Howe Island having since died out, cf. American Ornithologists' Union (1983).

Tyto capensis (Smith, 1834)—Despite the tendency to treat Asian-Australian populations of the Grass Owl (longimembris Jerdon, 1839) as specifically distinct from African capensis Smith, 1834 (Condon 1975; Bruce in White & Bruce 1986; Sibley & Monroe 1990), no case has been made for this arrangement other than by Sharpe (1875). He distinguished them by the presence or absence of bars on the primaries and tail, traits that are inconsistent in the group (Schodde & Mason 1981: 88). Relationships need re-evaluation before these two major regional forms are split, a point implicit in Mees (1964) who used longimembris Jerdon, 1839 for Australian populations only because he interpreted it as the senior available name for the group. Although there appears to be only one form in Australia, core isolated populations in inland Australian, coastal northeast Queensland and Northern Territory need to be compared for verification.

Tyto multipunctata Mathews, 1912—This particularly small and black-and-white north-east Queensland form is kept specifically distinct from T. tenebricosa (Gould, 1845) following the last substantive analysis of its traits (Schodde & Mason 1981: 69, cf. Mees 1982). Relationships between the two forms and the sootier T. tenebricosa arfaki (Schlegel, 1879) of New Guinea need re-examination. Sibley & Monroe (1990) referred arfaki to multipunctata, contrary to the analysis in Schodde & Mason (loc. cit.).

Tyto novaehollandiae (Stephens, 1826)—Australian members are part of a complex of forms which is centred in Australo-Papuasia and extends north-west to Sulawesi and the Sula Islands and north and north-east to the Admiralty Islands (Manus) and New Britain, see Stresemann (1933, 1934), Eck & Busse (1973), Schodde & Mason (1981), White & Bruce (1986), and Sibley & Monroe (1990). Which taxa to include in T. novaehollandiae (Stephens, 1826) and which to separate specifically are questions still far from resolution. Here Australian members are all treated as subspecies of novaehollandiae, as is conventional, see Peters (1940), Mees (1964), Condon (1975), and Schodde & Mason (loc. cit.). In separating Tasmanian T. n. castanops (Gould, 1837) allospecifically, Sibley & Monroe (1990) followed the unsubstantiated opinion of McAllan & Bruce (1989).
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Diagnosis

Medium-sized, speckle-plumaged raptors, with forward-facing deep brown eyes in discrete facial discs, and hooked and cered bills surrounded by facial bristles; body feathering soft and downy in defined tracts; no under downs; aftershafts vestigial; uropygial gland well developed, tufted. Feet taloned and anisodactylous; tarsi feathered with feathers reversed on plantar-tarsi, outer toe reversible, mid toe equal to inner, with pectinate claw; hypotarsus with single deep furrow. Sexes similar or females larger. Wings broadly rounded with emiges frayed on forward edge only: 10 inemarginate primaries plus remicle and 12–18 diastataxic secondaries moulting erratically; tail short, emarginate: 12 rectrices moulting erratically in somewhat centrifugal sequence. Nares holorhinal and impervious, nasal septum imperforate; schizognathous (-desmognathous) palate, with small discrete vomer, straight and uniformly expanded palatines almost concealing unswollen maxillaries free fromexpanded lachrymals; basipterygoid processes developed; skull anteriorly flattened with median furrow, with moderately large orbits separated by much thickened septum; cervical vertebrae 14, the neck flexible and able to turn through about 270º; sternum very broadly and shallowly one-notched on either side, only rudimentary spina externa present if at all, furcula unexpanded at articulation with coracoids, without hypocleideum. Musculus expansor secundariorum and biceps slip absent, M. tensor patagium brevis with wristward slip; pelvic muscle formula A or AD, no M. ambiens, deep plantar tendons Type I. Carotid arteries paired. Syrinx bronchial, with one pair of intrinsic muscles attached to rings 1–10. Eyes moderately large, tubular, closed by both lids, the upper with a flap; ears long, with large flap covering small orifice; tongue fleshy; no crop; caeca large, dilated. Diploid karyotype of 90 chromosomes, without macrochromosomes.