Family STRIGIDAE

Nionox (Rhabdoglaux) strenua

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Family STRIGIDAE

Compiler and date details

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

Introduction

Strigidae (typical or hawk owls) comprises about 123–161 species in 22–27 genera; six species in one genus occur in Australia and its territories. The Australian fossil record is limited to Ninox Hodgson, 1837 in the Holocene-Pleistocene on Norfolk Island and in southern Victoria. The family is virtually cosmopolitan, with centres of diversity in North and South America, Eurasia and Africa.

Strigid owls are nocturnal or sometimes crepuscular predators that, solitary, in pairs or family groups, roost by day with head erect in trees, hollows, holes or burrows, and sally on wing at night to catch large insects or small vertebrates in their talons, swallowing prey usually in large dismembered pieces or sometimes whole at perch, and regurgitating indigestible parts in medium-sized, loosely bound pellets. Nests are of unconstructed beds in hollows, holes, burrows or usurped platform nests of other birds; eggs are spheroidal, plain dull white, and are incubated by the female; young are altricial, nidicolous and moult through two successive downs (protoptile, mesoptile) to fledge in the second.

Family-group Systematics

Whether to combine the strigid and tytonid owls in one family, or to separate them in two, remains open to argument. Hartert (1912–1921), Stresemann (1927–1934), Mayr & Amadon (1951), Vaurie (1965), Eck & Busse (1973), Wolters (1975–1982) and Amadon & Bull (1988) combined them, an approach supported by morphological and ontogenetic evidence (Stresemann & Stresemann 1966; Bock & McEvey 1969), cross-fertility (Flieg 1971), and the traits of the bay owls, Phodilus Geoffroy Saint-Hilaire, 1830 (Beddard 1890; Pycraft 1903a; Stresemann loc. cit; Miller 1965; Burton 1973; Eck & Busse loc. cit.; cf. Marshall 1966). Alternatively, strigids and tytonids have been separated in two families by Sharpe (1875), Beddard (1888), Pycraft (1898,1903b), Peters (1940), Verheyen (1956), Wetmore (1960), Mees (1964), van der Weyden & Ginn in Burton (1973), Condon (1975), Clark et al. (1978), Schodde & Mason (1981), American Ornithologists' Union (1983), Cramp (1985), Sibley et al. (1988) and Sibley & Monroe (1990); Phodilus has usually been included with the tytonids. Although strigids and tytonids may be monophyletic with respect to other families, prevailing convention supported by the genetic distance recorded between them by DNA/DNA hybridisation (Sibley et al. loc. cit.; Sibley & Ahlquist 1990), and the widely divergent karyotype of tytonids, including Phodilus (data in Christidis 1990), suggest that they are better treated as separate families for the present. This arrangement is consistent with their usual treatment in Australian literature cf. Alcedinidae.

By convention, strigid owls comprise two subfamilies: New World and Eurasian Striginae Leach, 1820 with large asymmetric ears and well-developed facial discs, and cosmopolitan Buboninae Vigors, 1825 with smaller, symmetric ears and incomplete to obscure facial discs (e.g. Sharpe 1875; Peters 1940; Cramp 1985). Buboninae are much the larger group, and include Australasian Ninox Hodgson, 1837. Wolters (1975–1982) and tentatively C.S. Roselaar in Cramp (loc. cit.) have split Strigidae as defined here into three subfamilies but with differing limits, indicating that infra-familial groupings and phylogeny are far from understood.

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

Genus-group Systematics

Ninox Hodgson, 1837—As accepted here, this genus comprises about 16–19 species of west Pacific owls with small, untufted inoperculate ears, obsolete facial discs, and simple descendent moult of primaries. These traits suggest that their closest relatives are Asian-American Athene Boie, 1822, Glaucidium Boie, 1826 and related owls, including Sceloglaux Kaup, 1848, from which they are distinguished by the rather trivial characters of a longer and more pointed wing, shorter first primary and more restricted nocturnal activity (cf. Sharpe 1875; Eck & Busse 1973). The relationships of these genera need further clarification, as do the subgeneric groups in Ninox and the supposedly related Uroglaux Mayr, 1937 in New Guinea, cf. Schodde & Mason (1981: 37). All three subgenera of Ninox recognised here are present in the Australasian region, the centre of diversity for the genus.

Species-group Systematics

Ninox boobook (Latham, 1802)—Although this Australian-centred species has been treated conventionally as conspecific with N. novaeseelandiae (Gmelin, 1788), it is kept separate here after Schodde & Mason (1981: 58) because its distinguishing traits of proportion and pattern have received only passing appraisal since, cf. Mees (1982) and White & Bruce (1986). In north-eastern Queensland, N. b. lurida (De Vis, 1887) may also be distinct specifically (Schodde & Mason loc. cit.), but evidence of sympatry with other forms of N. boobook is needed.

Ninox novaeseelandiae (Gmelin, 1788)—The forms of boobook owls on Lord Howe and Norfolk Islands are members of the N. novaeseelandiae (Gmelin, 1788) superspecies (Mees 1964), but their relationships to either N. novaeseelandiae, sensu stricto, or the allospecific N. boobook (Latham, 1802) have not been determined, see Schodde & Mason (1981). Accordingly, they are kept here as subspecies of N. novaeseelandiae as is conventional. This procedural decision is supported by data on their proportions and plumage patterns in relation to morphological differences between N. novaeseelandiae and N. boobook catalogued by Schodde & Mason (loc. cit.: 58):

(1) Lord Howe Island form (n=12)—tail/wing ratio 0.62±0.01, primaries 1 8, 2 6, 3 ‹ 5, facial disc light red-brown and concolorous with dorsum;

(2) Norfolk Island form (n=9)—tail/wing ratio 0.63±0.01, primaries consistently 1 ‹ 8, 2 ‹ 6, 3 ‹ 5, facial disc chestnut-brown with faint greyish cast and concolorous with crown.

The relationships of these island forms, however, need closer scrutiny.

Ninox squamipila (Bonaparte, 1850)—In its conventional definition, as adopted here, Ninox squamipila (Bonaparte, 1850) comprises two widely separated groups of populations. One ranges from the Moluccas to Tanimbar in the eastern Banda Sea where it is represented by four subspecies (White & Bruce 1986), and the other is endemic to Christmas Island in the Indian Ocean. Notwithstanding the differences recorded by Olsen & Stokes (1989), the Christmas Island population shares with east Banda Sea forms a complement of traits not found in other small species of Ninox: medium-large size (among the small Ninox) with relatively long tail, rusty-rufous body plumage including uniform throat, closely rusty-and-white barred lower ventrum, plain head and mantle grading to geographically differentiated white spotting or barring over wings to lower back, and closely barred tail (from material in AMNH, ANWC); there is no difference in iris. If the Christmas Island population is of separate origin from Banda Sea squamipila, as is quite possible, then the extent of morphological convergence between them is extraordinary. Relationships between the two groups need further investigation to settle their status.

Ninox connivens (Latham, 1802)—For Australian populations, the most recent revision by Ford (1986) is not followed here because, although distinguishing Cape York Peninsula populations from those to the south, it does not compare their statistics in size with others from elsewhere in northern Australia, and does not analyse regional variation in colour cf. Schodde & Mason (1981: 52).

Ninox rufa (Gould, 1846)—Circumscription of this species, including New Guinean forms and excluding the Powerful Owl (Ninox strenua (Gould, 1838)), was first established by Mathews (1916: 352–353) who synthesized the various opinions of C.W. De Vis, A.J. North and Ernst Hartert.

Excluded Taxa

Vagrant Species

STRIGIDAE: Ninox connivens assimilis Salvadori & D'Albertis, 1876 [Included in some Australian checklists, possibly vagrant to Torres Strait]

CAVS:8951
STRIGIDAE: Ninox japonica japonica (Temminck & Schlegel, 1844) [Brown Hawk-Owl; vagrant to Ashmore Reef and WA. Specimen record from Ashmore Reef in January 1973, see Schodde & Van Tets (1981). Accepted by RAOU Records Appraisal Committee (1988: case no. 17). The specimen appears to be of the east Asian subspecies, N. s. japonica (Temminck & Schlegel, 1844) which migrates to the Philippine and Indonesian archipelagos during the boreal winter, see Mees (1970)] — Mees, G.F. 1970. Notes on some birds from the island of Formosa. Zoologische Mededelingen (Leiden) 44: 285-304; Schodde, R. & Van Tets, G.F. 1981. First record of the Brown Hawk-Owl Ninox scutulata from Australasia. The Emu 81: 171; RAOU Records Appraisal Committee 1988. Second Report of the Records Appraisal Committee. The Emu 88: 54-57

CAVS:0823
STRIGIDAE: Ninox scutulata (Raffles, 1822) [Brown Hawk-owl; vagrant to Ashmore Reef and WA] — Stanger, M., Clayton, M., Schodde, R., Wombey, J. & Mason, I. 1998. CSIRO List of Australian Verebrates: A Reference with Conservation Status. Collingwood : CSIRO Publishing iii 124 pp. [97]

Diagnosis

Small to very large, mottled-plumaged raptors, with forward-facing usually yellowish eyes in usually weakly developed 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, naked. Feet taloned and anisodactylous; tarsi feathered, outer toe reversible, mid toe longer than inner, with smooth claw; hypotarsus with single deep furrow. Sexes similar, females usually larger. Wings broadly rounded with remiges frayed all round; 10 emarginate primaries plus remicle moulting in descending or serial sequence, and 12–18 diastataxic secondaries moulting at three foci; tail rounded: 12 (rarely 10) rectrices moulting erratically in somewhat centripetal sequence. Nares holorhinal and impervious, nasal septum imperforate; schizognathous (-desmognathous) palate, with small discrete vomer, palatines curved and posteriorly expanded, leaving swollen and pneumatic maxillaries and appressed lachrymals well exposed; basipterygoid processes developed, functional; skull bulbous, with huge orbits separated by thinseptum; cervical vertebrae 14, the neck flexible and able to turn through about 270º; sternum deeply two-notched on each side, only small spina externa present, furcula expanded 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 very large, tubular, closed by both lids; ears large, often asymmetric, with little covering flap; tongue fleshy; no crop; caeca large, dilated. Diploid karyotype of 78–82 chromosomes, with 6–7 pairs of macrochromosomes.