Ducula, HODGSON, 1836

GENUS DUCULA HODGSON, 1836 View in CoL

Remarks: This genus is widely distributed from Asia, through the Philippines, Melanesia and across Polynesia ( Dickinson & Remsen, 2013). The widespread Du. pacifica is the only extant member of the genus known from Tonga, although other extant species are known to the west in Fiji, Ducula latrans ( Peale, 1849) , and to the east in Society Islands and Tuamotu Archipelago, Ducula aurorae ( Peale, 1849) ( Dickinson & Remsen, 2013) .

In addition to such medium-sized pigeons, there existed formerly a suite of larger species of Ducula from New Caledonia to the Marquesas, although only the species at these two geographical extremes still survive: Du. goliath ( New Caledonia) and Du. galeata (Marquesas). Extinct populations or species of large Ducula , from west to east, include Ducula sp. cf. Du. goliath on Efate in Vanuatu ( Worthy et al., 2015), an undescribed Ducula sp. on Viti Levu and Ducula lakeba Worthy, 2001 on the Lau Group, Fiji ( Worthy, 2001), Ducula david Balouet & Olson, 1987 on Uvea in Wallis and Futuna ( Balouet & Olson, 1987), extirpated populations referred to as Du. galeata on the Cook Islands (Mangaia) and on the Society Islands (Huahine) ( Steadman, 1989a, b, 1995, 1997, 2006a), an undescribed species from Rapa Island in the Austral Group ( Tennyson & Anderson, 2012), Ducula tihonireasini Rigal et al., 2018 on Mangareva ( Rigal et al., 2018) and Ducula harrisoni Wragg & Worthy, 2006 on Henderson Island ( Wragg & Worthy, 2006). In addition to these populations or taxa, a large undescribed species of Ducula has been reported from several islands in Tonga [ Steadman, 1989a, 1993 (as Du. david ), 1995, 1997, 2006a].

IDENTIFYING TRAITS

Species of Ducula are easily distinguished on most limb bones from columbids of a similar size by the following diagnostic features ( Worthy, 2001; Wragg & Worthy, 2006; Worthy & Wragg, 2008; Rigal et al., 2018). The elements coracoid, tibiotarsus and tarsometatarsus are the most diagnostic; therefore, key features are listed here.

Coracoid: The sulcus m. supracoracoidei is not pneumatic; the tuberculum A (see terminology of Worthy, 2012) is large, abuts the facies articularis humeralis, does not abruptly overhang the sulcus m. supracoracoidei and is widely separated from the insertion for the ligamentum acrocoraco-acromion acrocoracoid (ilaa); the tuberculum for ilaa has little projection over the sulcus m. supracoracoidei; the facies articularis clavicularis extends ventrally from the tuberculum for ilaa as a flattened facies to a large, sternally directed projection for the insertion for the ligamentum acrocoraco-procoracoideum (ilap) on its ventral margin; there is no crest overhanging the sulcus m. supracoracoidei connecting ilaa and ilap; sternally, the impressio m. sternocoracoidei extends close to the medial margin and has a large pneumatic foramen penetrating towards the angulus medialis; the facies articularis sternalis dorsalis is broad, especially medially, and a crest extends cranially from the angulus medialis, enclosing a distinct flattened area dorsally between it and the impressio m. sternocoracoidei and the facies articularis sternalis.

Tibiotarsus: The distal condylar width is about the same caudally and cranially; the depth of the condylus medialis is about equal to the distal condylar width; the medial tuberosity for the proximal attachment of the retinaculum extensorium tibiotarsi (ptRET) is prominent and is separated from the condylus medialis by a distance greater than the proximodistal height of that condyle; the distal attachment point for the retinaculum extensorium tibiotarsi (dtRET) forms a marked prominence on the lateral side of the sulcus extensorius proximal to the pons supratendineus; a sharp crest bounds the lateral margin of the sulcus extensorius proximal to the pons supratendineus; the medial attachment point for the retinaculum m. fibularis (mtRMF) laterad of the sulcus extensorius is poorly marked; the lateral attachment of the retinaculum m. fibularis (ltRMF) is aligned parallel to the shaft on the lateral facies; and it lacks a foramen penetrating the corpus cranially, close to the proximal margin of the condylus lateralis.

Tarsometatarsus: This is relatively short, with those of species of Columba shorter, and those of Alopecoenas , Caloenas , Didunculus , Gallicolumba and Goura all relatively longer; the cotyla medialis in medial view is projected dorsally; the medial foramen of the foramina vascularia proximalia is elongate and much larger than its lateral counterpart; the foramina vascularia proximalia are widely separated by a low ridge in a sulcus bounded by prominent ridges; the foramen vasculare proximale medialis lies close (less than the foramen width) to the medial edge of the shaft; the tuberositas m. tibialis cranialis is distal to the foramen vasculare proximale medialis in the sulcus extensorius and is therefore close to the medial margin; and the lateral profile of the shaft leading to trochlea metatarsi IV is slightly concave.

DUCULA PACIFICA (J. F. GMELIN, 1789) View in CoL , PACIFIC IMPERIAL PIGEON

Material: Hopoate: NISP = 22, MNI = 6. Nukuleka: NISP = 2, MNI = 1. Falevai: NISP = 2, MNI = 1. Ofu: NISP = 8, MNI = 2. Otea: NISP = 1, MNI = 1. Vuna: NISP = 20, MNI = 4.

Remarks: Ducula pacifica is widespread in the tropical Pacific, with a range extending from the Bismarcks and New Guinea east through the Solomons, Vanuatu, Fiji, Tonga and Samoa to Niue and the Cook Islands ( Steadman, 2006a; Dickinson & Remsen, 2013). In Fiji, Du. pacifica is found only on small islands, but the endemic Du. latrans typical of the larger islands is sympatric with Du. pacifica on some smaller islands ( Watling et al., 2001; Steadman, 2006a). In Tonga, Du. pacifica is the only resident member of this genus now, but Steadman (2006a: 335) stated that it ‘coexisted … with two larger, extinct or extirpated congeners, D. latrans and D. undescribed sp., even on small, flat islands in the Ha'apai Group’. However, based on the data available to us, Du. pacifica and Du. latrans broadly overlap in all skeletal measurements (Appendices 2 and 3); therefore, we do not know how the two species were separated. In the Tongan fossil sample, although the bones are rather fragmented, as is typical of archaeological faunas, all fall within a narrow size range, in part captured by measurements below and in Appendices 2 and 3, and no evidence was seen to suggest that two taxa might be represented. Therefore, all bones are assumed to represent the extant species of Ducula in Tonga, i.e. Du. pacifica . The other large species of Ducula is much larger and is considered separately below. Ancient mounds and oral traditions recording the construction of platforms from which to snare Pacific pigeons show the cultural significance of these birds in prehistoric times throughout Tonga ( Burley, 1996).

Measurements: See Appendices 2 and 3. Coracoid: length from base of cotyla scapularis to top of acrocoracoideus, mean 12.1 mm, range 11.5–13.2 mm, SD = 0.60, N = 10; minimum shaft width, mean 3.6 mm, range 3.3–3.9 mm, SD = 0.16, N = 17. Ulna : SW 3.6, 3.8 mm; width of condylus dorsalis, 6.5, 7.0 mm. Carpometacarpus: PW 10.1 mm. Femur: PW 8.4, 8.9, 9.0, 9.1 mm. Tarsometatarsus: shaft width fossa metatarsi I, mean 4.3 mm, range 4.3 mm, N = 3; depth of trochlea metatarsi III, mean 3.8 mm, range 3.2–4.9 mm, SD = 0.58, N = 6.

COLUMBID MAGN. DUCULA PACIFICA (J. F. GMELIN, 1789) , PACIFIC IMPERIAL PIGEON

Material: Hopoate: NISP = 3, MNI = 2. Nukuleka: NISP = 11, MNI = 4. Ofu: NISP = 4, MNI = 1. Otea: NISP = 2, MNI = 1. Vuna: NISP = 31, MNI = 6.

Remarks: These specimens are either too incomplete or otherwise undiagnostic for confident generic attribution among columbids and are therefore referred only to columbids, but their size conforms with that of Du. pacifica .

DUCULA SHUTLERI WORTHY & BURLEY SP. NOV., SHUTLER'S FRUIT PIGEON

( FIG. 4)

h t t p:/ / z o o b a n k. o r g / u r n:l s i d: z o o b a n k. o r g: a c t: C7BC1177-FC61-4BA8-8BBC-C770C6884A20

Holotype: NMNZ S.48354, field number Of 1.05.12.08, left tarsometatarsus, collected by David Burley et al. on 6 June 2005 ( Fig. 4A).

Paratypes: NMNZ S.48355, field number Of1.05.21.09, distal right tarsometatarsus preserved distal to metatarsal facet ; NMNZ S.48356, field number Of1.05.22.04, left tarsometatarsus minus trochlea; NMNZ S.48357, field number Of1.05.22.09, distal left tarsometatarsus ( Fig. 4B).

Etymology: Richard Shutler Jr was an early pioneer in Oceanic archaeology, and in 1952 excavated, with Edward Winslow Gifford, at the eponymous Lapita site (Site 13) in New Caledonia ( Sand & Kirch, 2002). He was instrumental in introducing David Burley to Pacific archaeology in the early 1990s and was a part of Burley's Tongan field projects in the 1990s and early 2000s.

Type locality: Layer 8, 70–80 cm depth, Unit 12, Ofu site, Ofu Island, Vava'u Group, Tonga.

Diagnosis: A species of Ducula with tarsometatarsus much longer than the largest extant species ( Du. galeata of the Marquesas and Du. goliath of New Caledonia) or the extinct Du. tihonireasini of Mangareva and Du. david of Uvea, but of equal length to those of Du. harrisoni of Henderson Island and Du. lakeba of Fiji (see Table 7). Tarsometatarsus is more robust than those of Du. harrisoni and Du. lakeba and all other large species of Ducula except that of Du. david , as defined by proximal width and maximal shaft width across the articular facet in fossa metatarsi I as a proportion of length ( Table 7). The dorsal medial lineae intermusculari is weakly marked distal to the metatarsal facet, and the shaft is relatively compressed dorsal to fossa metatarsi I.

Measurements (in millimetres): Holotype NMNZ S.48354 (Of1.05.12.08). Total length, 47.6; length to proximal margin foramen vasculare distale, 37.0; length to distal side of the metatarsal facet, 28.8; length from posterior edge cotyla medialis to proximal end of fossa metatarsi 1 (length 2 of Wragg & Worthy, 2006), 23.2; length from posterior edge of cotyla medialis to distal end of medial prominence of fossa metatarsi 1 (length 3 of Wragg & Worthy, 2006), 27.4; proximal width, 13.8; shaft width at metatarsal facet, 6.2; least shaft width distal to metatarsal facet, 5.5; width of trochlea metatarsi III, 4.3; depth of trochlea metatarsi III, 5.0.

Paratypes: See Table 7 and NMNZ S.48355 (Of1.05.21.09), dR tmt, depth of trochlea metatarsi III, 5.0; NMNZ S.48356 (Of1.05.22.04), L tmt, preserved length, 41.2; NMNZ S.48357 (Of1.05.22.09), 1dL tmt, preserved length, 36.3; depth of trochlea metatarsi III, 5.1.

Referred material: Ducula shutleri Hopoate : Hop.14.TP2.06, sL tmt; NISP = 1, MNI = 1. Falevai: Ka2.05.03.15a, L scap; Ka2.05.XX.00FE0a, sR tmt; NISP = 2, MNI = 1. Ofu: Of1.05.11.05, R scap; Of1.05.12.06, L cor, sR tmt; Of1.05.12.07, L scap, dL cmc, sL tmt; Of1.05.12.07, pR fem; Of1.05.12.08, R scap, cran and sternal pts L cor, 2sR cor, dL tib; Of1.05.12.09, dR tib, dR tmt; Of1.05.12.10, ant stern, R scap, cran and sternal pts 1 R cor, sternal pts LandR cor, pL fem; Of1.05.20.06, pL fem; Of1.05.20.06, L scap; Of1.05.20.07, R tib (missing proximal end and distal condyles); Of1.05.20.07, sternal pt L, cran pt L cor; Of1.05.20.07, L fem; Of1.05.20.08, dL tib, sR tmt, pR ulna, R MII.1; Of1.05.20.09, 3pL1dR fem; Of1.05.20.09, 2L scap; Of1.05.20.10, cran pt R cor, L scap, dL tib; Of1.05.21.06, R (-d) fem; Of1.05.21.08, sL tmt; Of1.05.21.08, pR dL rad; Of1.05.21.09, R scap; Of1.05.21.10, s+dR tmt, sR tmt; Of1.05.21.10, s+pL sL ulna; Of1.05.21.10, R scap; Of1.05.21.10, dR ulna; Of1.05.21.10, pR fem; Of1.05.21.11, cran pt R cor; Of1.05.22.04, sR cor; Of1.05.22.05, pLdL cmc; Of1.05.22.07, pR rad, dL cmc, L scap, 1sR cor, sR tib, sL tmt; Of1.05.22.08, pLdL rad, L scap; Of1.05.22.09, 2pL3dL tmt, 1 R one cran pt R one sternal pt R cor; Of1.05.22.09, 2pL rad, R scap; Of1.05.22.10, two cran pt L 1 R cor, pt pL dR tmt; Of1.05.22.10, 3pL1dL fem, 2sR tib, 1dL cmc; including type material NISP = 93, MNI = 11. Vuna: Pa1.04.12.08, pL fem; Pa1.04.12.10, R scap; Pa1.04.22.04, pL fem medullary bone; Pa1.04.23.09, dR tmt; Pa1.04.24.09, pR fem; NISP = 5, MNI = 2 .

Tentatively referred material: Identified as ‘Columbid lge, cf. Ducula ’. Ofu: Of1.05.12.05, pLdR rad, dLdR ulna, two ulnar shaft frags; Of1.05.12.06, sL ulna, 2sR tib; Of1.05.12.08, d+sR rad, pR rad; d+sL sL sR d+sR cmc; Of1.05.12.09, 3dL cmc, sL ulna, sL tib; Of1.05.12.10a, sR hum, sL ulna; Of1.05.14.08, sL fem; Of1.05.15.05, dR rad; Of1.05.20.06, sR fem; Of1.05.22.05, L scap, dL rad; Of1.05.22.06, 3pL two pt shaft ulnae, two pts 1L cor, pt R cmc, 2 R scap, 1dR rad, 2sR1sL tib, sLsR fem, pt sR tib; Of1.05.22.09, 1dL rad, sLsR tib, pmx; Of1.05.22.10, 1dL2dR cmc; NISP = 51, does not alter Ofu MNI. Vuna: Pa1.04.12.11, sR tmt; Pa1.04.17.08b, sR cor; Pa1.04.24.09, sL tmt; NISP = 3, MNI for Vuna unchanged by these.

Description and comparison

In addition to the diagnostic features described above, Du. shutleri has the following features.

Humerus: Humeri are represented by a part of a right shaft Of1.05.12.10a with a minimum dorsoventral width of 8.5 mm, which lacks diagnostic features. However, it is larger and more inflated craniocaudally than the Caloenas specimens described above, e.g. the dR humerus in lot Of1.05.12.10. The specimen tentatively referred to Du. shutleri is larger than MNZ S.37316, a specimen of an undetermined large species of Ducula from Vitilevu, available specimens of Du. lakeba (see Worthy, 2001: table 8) and those of Du. harrisoni , which apparently had somewhat diminutive wings ( Wragg & Worthy, 2006).

Ulna : The most informative ulnar specimens are a well-preserved proximal third of a bone (Of1.05.20.08, Fig. 4F, PW = 11.2 mm, least SW = 6.3 mm) and a distal right ulna (Of1.05.21.10, DW = width 11.0 mm, width of condylus dorsalis 10.1 mm). These reveal that the ulna is rather larger than those referred to Caloenas carpometacarpus Of1.05.22.05, in ventral view. H, left coracoid missing most of processus acrocoracoideus Of1.05.22.10, in dorsal view. I, omal end of left coracoid Of1.05.22.10, in dorsal view. Scale bars: 10 mm. Abbreviations: artic., articularis; dtRET, the distal attachment point for the retinaculum extensorium tibiotarsi; ilaa, insertion for the ligamentum acrocoraco-acromion acrocoracoid; ilap, insertion for the ligamentum acrocoraco-procoracoideum; proc., processus; ptRET, the medial tuberosity for the proximal attachment of the retinaculum extensorium tibiotarsi; tub. A, tuberculum A; tub. m., tuberositas musculus.

Data are from Worthy (2001), Wragg & Worthy (2006) and Rigal et al. (2018). The PW /L2 and SWmf/L2 ratios are given as percentages. Abbreviations: DW, distal width; Ldmf, length to distal side of the metatarsal facet from eminence intercotylaris; L2, length from posterior edge cotyla medialis to proximal end of fossa metatarsi 1 (length 2 of Wragg & Worthy, 2006); L3, length from posterior edge cotyla medialis to distal end of medial prominence of fossa metatarsi 1 (length 3 of Wragg & Worthy, 2006); PW, proximal width; SWdm, least shaft width distal to metatarsal facet; SWmf, shaft width at metatarsal facet; TL, total length; WTIII, width of trochlea of metatarsi III.