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New prehistoric avifaunas from the Gambier Group, French Polynesia

This paper analyses 647 bird bones identifiable at least to family-level collected from archaeological sites in 2005, 2012 and 2014 by P. Kirch, in the Gambier Group, French Polynesia. The bones derive from Onemea Site (TAR-6) on Taravai Island, Nenega-Iti Rock Shelter (AGA-3) on Agakauitai Island and Kitchen Cave (KAM-1) on Kamaka Island. Eighteen bird species, four newly recorded in this archipelago, are represented among the bones from archaeological layers dating from human arrival in the tenth century to the late pre-European contact period in the early nineteeth century. They reveal that the original avifauna from the Gambier Group minimally included 37 species. These include six now extinct taxa, a species of Pseudobulweria petrel, two columbids ( Bountyphaps obsoleta , Ducula tihonireasini n.sp. described herein) and three other land birds that were recorded historically. Minimally, a further six species have been extirpated from the Gambier Group. These archaeological avifaunas are strongly dominated by seabirds (89.4% Minimum Number Individuals) but differences in species representation and dominance suggest the composition of breeding seabird faunas differed between islands. Columbidae were the dominant land birds (58.9% MNI), although no species of this family currently exist on this archipelago.


INTRODUCTION
Extinctions, especially of birds, have often been the unintended consequence of human arrival on islands and the subsequent environmental changes resulting from human activities such as hunting, forest clearance, and habitat disturbance (Steadman, 2006;Kirch, 2007;Hume and Walters, 2012;Walther and Hume, 2016). Historical occurrence data has often documented many of these extinctions (Greenway, 1958;Fuller, 1987), but for many oceanic islands such historical records are lacking, so study of osseous remains is the only way to assess former diversity. However, due to the scarcity of suitable fossil deposits, the study of the archaeological record often provides the primary insight into the pre-human avifaunas. This is especially true for the Polynesian islands of the Pacific where the uneven geographic coverage of Pacific-wide archaeological investigations prevents biogeographers from fully appreciating human influences on the distribution of species, especially for birds (Steadman, 1997(Steadman, , 2006, and therefore restricts our understanding of the evolution of the fauna. The Gambier Group lies in the southeast corner of French Polynesia, 180 km southeast of the Acteon Group in the Tuamotu Archipelago and 540 km northwest of Henderson Island, on the Tropic of Capricorn about midway between Australia and South America, see maps in Steadman (2006) and Thibault and Cibois (2017) showing the geographical context of the group within eastern Polynesia. Here we use the term Gambier Group for the entire set of 14 islands and islets that are encompassed within a barrier reef and lagoon to form a near atoll ( Figure 1). The old and high (441 m) island of Mangareva (14 km 2 ) and the 13 smaller associated islands are volcanic in origin. The Tuamotu-Gambier Archipelago owes its existence to the Pitcairn volcanic hotspot, which resulted in volcanic activity between 25 m.y.a. and 500 k.y.a. (Bonvallot et al., 1993;Hekinian, 2003). As the Pacific Plate advanced to the northwest across this hotspot, the volcanic islands of the Gambier Group were the penultimate group to be formed, between 6.0 and 4.8 m.y.a. (Bonvallot et al., 1993), with Pitcairn Island the most recent land to emerge from this volcanic activity. After Mangareva, Taravai (256 m, 5.3 km 2 ), Akamaru (2 km 2 ), Aukena (1.5 km 2 ), Agakauitai (0.7 km 2 ) and Kamaka (0.5 km 2 ), are the five next largest islands in the Gambier Group. All of these islands including some islets (motu) are separated by relatively shallow water, but would have formed continuous land during most of the Pleistocene.
Archaeological research has revealed that the human pre-European colonization of the Polynesian region occurred in two distinct phases separated by approximately 1800 years (Anderson, 2001(Anderson, , 2003Kirch et al., 2010;Kirch, 2017). The first phase occurred when people of the Lapita culture expanded eastwards from the Fijian archipelago to colonize the Samoa-Tonga area between 900-800 BC (Burley et al., 2012;Kirch, 2017:88, table 4.2). The second phase involved the expansion of Polynesians out of the Samoa-Tonga homeland into the central eastern Pacific beginning around AD 950, leading to the colonisation of the Society Islands, the Marquesas, Mangareva, the Pitcairn-Henderson group and Easter Island by approximately AD 1100 (Anderson and Sinoto, 2002;Conte and Anderson, 2003;Kirch, 2017:198-200, table 7.2). The more remote Hawaiian archipelago was settled between AD 940-1130 (Athens et al., 2014), while New Zealand was not reached until AD 1140-1340 (Wilmshurst et al., 2008). Given these fairly recent dates for human arrival in the islands of eastern and marginal Polynesia, the impacts of humans on the avifaunas of the eastern Pacific are in all cases quite recent. With regard to the fossil avifauna of the Tuamotu Archipelago and Gambier Group, Steadman (2006: 235) wrote "The lack of bird bones from this region is a void in the avian prehistory of Polynesia that rivals that of Upolu and Savai'i, the two largest islands in Samoa." The first insight into the avian prehistory of the Gambier Group derived from Roger Green's pioneering archaeological research in 1959, when he excavated five sites on Aukena, Kamaka and Mangareva dating to the eleventh to seventeeth centuries AD (Weisler, 1996;Green and Weisler, 2000Steadman and Justice, 1998;Steadman, 2006: 236;Kirch, 2004, 2008). Green's excavations produced 215 identifiable bird bones, although only four were of native land birds (Steadman and Justice, 1998;Steadman, 2006). A new archaeological campaign launched by P. E. Conte in 2001 and2003 resulted in the discovery of abundant bird bones, especially in the Onemea or TAR-6 site on Taravai Island (166 identified in test pit 2 at TAR-6; Worthy and Tennyson, 2004), foreshadowing the acquisition of a significant sample informing on the former Gambier avifaunas. The rich avifauna and associated early radiocarbon dates suggested that the Onemea site was likely to have been a pioneering settlement (Conte and Kirch, 2004;Conte et al., 2004;Kirch and Conte, 2009). Further investigations at TAR-6 in 2005 greatly expanded the sample of bird bones, and taphonomic analyses of about half of the 1185 recovered bird bones or fragments showed that they derived from birds that humans had consumed (Kirch et al., 2010). Analyses of other faunal remains indicate that the earliest colonisers introduced the Pacific rat (Rattus exulans) and probably pig to Taravai (Swift et al., 2016). Additional field campaigns by Kirch in 2012 and 2014 expanded the initial test excavation in site AGA-3 on Agakauitai Island, and re-excavated the Kitchen Cave (KAM-1) site on Kamaka Island first dug by Green; avifaunal remains were recovered from both of these sites. Here we report on the total available avifaunas from the TAR-6, AGA-3 and KAM-1 sites, and present data on 647 bones identifiable to family-level or lower taxon levels, in total representing minimally 192 individuals.

Excavated Sites
The TAR-6 site on Taravai Island is a small calcareous dune at the head of Onemea Bay, on the island's southwest coast. Two test pits were excavated in 2003, revealing a rich concentration of bird bones at the cultural/pre-cultural stratigraphic interface (Conte and Kirch, 2004). This led to expanded excavations in 2005, with an additional 10 units being dug, resulting in a total excavated area for the TAR-6 site of 12 m 2 (Kirch et al., 2010). The greatest concentration of bird bones, however, came from the initial test pit (TP) 2, and from three adjacent units  that formed a 1 by 3 m trench at the top of the dune, situated close to TP-2. In these four units, the stratigraphy consisted of a thin, organically enriched loam (Layer I) overlying a reddish-gray, charcoalenriched cultural deposit (Layer II) about 60 cm thick, which in turn overlies a reddish-yellow aeolian sand (Layer III) generally lacking charcoal but containing a high frequency of bird bones.
Although not a midden deposit, the upper part of Layer III was clearly deposited after the arrival of Polynesians on the island, as this deposit contains the bones of human-transported rats (Rattus exulans) and landsnails (Allopeas gracile) along with a few basalt flakes and pieces of worked pearl shell. Eleven radiocarbon dates were obtained from the TAR-6 site, and bracket initial human activity at the site between approximately AD 900-1100. The main cultural deposit (Layer II) accumulated between AD 1200-1400 (Kirch et al., 2010, table 1). This deposit also contains bird bones, although the density is considerably less than that in Layer III.
The Nenega-iti rockshelter (site AGA-3) lies at the base of the steep volcanic ridge on the northwestern side of Agakauitai Island, about 100 m from the present shoreline. A mere overhang with a surface area of about 35 m 2 inside the dripline, the shelter nonetheless has well-stratified deposits with evidence of substantial occupation. A single test pit excavated in 2003 (Conte and Kirch, 2004:87-90) did not fully penetrate to the deepest occupation deposits. In 2012, an excavation of 9 m 2 exposed a significantly expanded sample (Kirch et al., 2015). In particular, the D9/E9/F9 trench exposed a 40-50 cm thick cultural deposit (Layer IV) with considerable numbers of bird bones near the base and at the interface with the underlying pre-cultural deposit (Layer V). Seven radiocarbon dates (Kirch et al., 2015, table 1, figure 7) indicate initial occupation beginning around AD 1300, with use of the shelter continuing up until the early post-European contact period.
The large Kitchen Cave rockshelter (KAM-1) on Kamaka Island, first excavated by Green in 1959, was re-examined by Kirch and his team in 2012, revealing well-stratified deposits in an area 4 adjacent to Green's original excavation. In 2014, this test pit was expanded with an additional 4 m 2 , for a total of 5 m 2 . The 2012-2014 excavations have yet to be published in full, but a series of 13 radiocarbon dates indicates initial occupation beginning around AD 1300 and more-or-less continual use of the rockshelter (probably intermittently) until European contact. The occupation sequence at KAM-1 thus closely parallels that at AGA-3.

Methods
We examined bird bones from three sites as follows: 1185 bones from Onemea (Site 190-12-TAR-6) on Taravai Island, 386 bones from Nenega-Iti Rock Shelter (Site 190-02-AGA-3) on Agakauitai Island and 280 bones from Kitchen Cave (Site 190-04-KAM-1) on Kamaka Island, collected by P. Kirch et al. in 2005Kirch et al. in , 2012 and 2014 respectively. The bones previously reported from the Onemea and Nenega-Iti sites (Worthy and Tennyson, 2004) were re-examined and integrated in the analysis. In total, the collection comprised 647 bird bones identified to family or lower taxon levels and 1362 unidentifiable bird bone fragments. The collections are mainly curated at the Service de la Culture et du Patrimoine, overseen by the Ministry of Culture, Government of French Polynesia, Tahiti, but a small series was deposited in the Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand, to facilitate taxonomic comparisons.
Specimens were examined under magnification with a binocular microscope for anatomical features and to compare to reference specimens. Comparisons were made with modern skeletons where possible or to the material reported by Worthy and Tennyson (2004), which was identified with reference to the extensive seabird skeletal holdings in the Museum of New Zealand Te Papa Tongarewa (Wellington, New Zealand). In particular, the bones previously identified as Pseudobulweria species (Worthy and Tennyson 2004) were our primary reference material for this taxon.

Comparative Materials
Skeletons from the South Australian Museum (SAM) and bones from the 2003 archaeological campaign, previously described by Worthy and Tennyson (2004), were used to identify the bones. Reference skeletons used in the identification of these bones are listed here.

Nomenclature
We followed the taxonomic nomenclature in Dickinson and Remsen (2013). The procellariids that occur in the eastern tropical Pacific Ocean fall into three size classes; small, medium and large (e.g., Brooke, 1995a;Pyle et al., 2011).
Among small shearwaters, the Tropical Shearwater Puffinus bailloni dichrous, here including P. bailloni polynesiae of Tahiti, is recorded on islands across the Pacific from Palau and the Marianas to the Gambier Group (Thibault and Bretagnolle, 1999;del Hoyo et al., 2017) and is known to breed in the Tuamotu Archipelago (Thibault and Cibois, 2012;del Hoyo et al., 2017). However, several other small shearwaters either probably did or still do forage in the non-breeding period in the Tuamotu Archipelago, and in some cases may have formerly bred there, e.g., Puffinus bailloni gunax (breeding Vanuatu), Townsend's Shearwater P. auricularis myrtae (=P. newelli myrtae in del Hoyo et al. (2017); breeding on Rapa Island; BirdLife International 2017), and Little Shearwater Puffinus assimilis kermadecensis (Pyle et al., 2011;BirdLife International 2017;del Hoyo et al., 2017). Among larger shearwaters, the breeding range of Christmas Shearwater Puffinus nativitatis spans the tropical central and eastern Pacific, including the Gambier Group and the Pitcairn Islands (Brooke, 1995b;Thibault and Bretagnolle, 1999;del Hoyo et al., 2017). The Wedge-tailed Shearwater Ardenna pacifica is known to breed in the eastern Pacific (Marquesas) (Thibault and Cibois, 2012;del Hoyo et al., 2017), so can also be expected, if only as a visitor, in the Gambier Group.
This issue of multiple similar-sized co-occurring taxa is especially problematic among Pterodroma petrels. Minimally, five small taxa frequent the tropical eastern Pacific. Gould's Petrel Pterodroma leucoptera leucoptera (breeding on islands off the coast of New South Wales, Australia), P. leucoptera caledonica (breeding in New Caledonia), Collared Petrel P. brevipes (breeding in Fiji and Vanuatu), and Pycroft's Petrel P. pycrofti (breeding off Northland, in New Zealand), are all known to forage in this area (Dickinson and Remsen, 2013;Rayner et al., 2016;BirdLife International, 2017). Furthermore, P. leucoptera has unconfirmed breeding records from the Austral Islands and further east and Black-winged Petrel P. nigripennis, while breeding in the southwest Pacific, has a non-breeding range in the north and eastern Pacific (BirdLife International, 2017). Thus, all these small species of Pterodroma could occur in the Gambier Group on occasion.
Several medium-sized Pterodroma species breed in the eastern tropical Pacific (Pratt et al., 1987;Brooke, 1995;Thibault and Cibois, 2017), most of which are poorly represented in compara-tive recent skeleton collections, making specific identification of fragmentary bones difficult. These include Murphy's Petrel Pterodroma ultima, the Kermadec Petrel P. neglecta, and the slightly smaller Herald Petrel P. heraldica, all known to breed on islands in the southeast Tuamotu Archipelago, the Gambier Group, and the nearby Pitcairn Group . In addition, the Henderson Petrel P. atrata, while only known to breed on the Pitcairn Group (Brooke, 1995;Thibault and Cibois, 2017), is a potential vagrant to the Gambier Group. Similarly, the Phoenix Petrel P. alba, has a widespread breeding distribution in the eastern tropical Pacific, including the Marquesas and the Pitcairn Group , so vagrants to the Gambier Group would be expected. Given extinction has resulted in the loss of many breeding colonies of petrels since human colonisation, it is likely that more than one taxon each of small and medium petrels formerly bred in the Gambier Group, and certainly several would have and still do forage in the group. As noted by numerous authors, identification of petrels to genera based on skeletal elements is straightforward, but specific separation of congeneric similar-sized species, is often not possible on morphology alone (Wragg, 1995;Olson and Rasmussen, 2001;Tennyson et al., 2015). For example, Murphy and Pennoyer (1952: 1) noted that many of these species are so similar skeletally as to preclude their separation, stating "We have compared, for example, skulls of the species neglecta, arminjoniana, and ultima and can find no detail that would distinguish one from another." Identification is even more difficult with post cranial bones and is compounded by breakage as typifies archaeological deposits, and so specimens are often grouped into large, medium and small size groupings within genera (e.g., Murphy and Pennoyer, 1952;Walker et al., 1990;Wragg, 1995;Olson and Rasmussen, 2001;Cooper and Tennyson, 2008;Tennyson et al., 2015).
Given the diversity of similar-sized taxa either occurring or likely to have occurred in the Gambier Group region, we adopt a conservative approach and identify bones to genus and size categories as follows using the term magn. from the Latin magnitudino to indicate the approximate size of the bones in question without implying possible relationship, following Olson and Rasmussen (2001): Puffinus magn. P. bailloni (to include all small Puffinus taxa); Pterodroma magn. P. leucoptera (for small Pterodroma species); P. magn. P. heraldica (for mid-sized Pterodroma species).

Measurements
AGA3-D9-IV4-21-5-1C, dR tibiotarsus: distal width 8.9 mm, depth medial condyle 9.4 mm, depth of lateral condyle 8.2 mm. KAM1-B3TP1-V-3A-B, dR ulna: shaft width 3.3 mm; maximum distal width >6.2 mm (tuberculum carpale broken). KAM1-B3TP1-VI-4A-F, distal shaft L tarsometatarsus, minimum shaft width proximal to metatarsal facet 3.85 mm. Comments. The tibiotarsus NMNZ S.47666 (Figure 2) from Nenega-Iti is referred to Bountyphaps and tentatively to B. obsoleta, described from Henderson Island, as it has the following unique combination of diagnostic features of that taxon (Wragg, 2008). 1) 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 much less than the height of the medial condyle; 2) the distal attachment point for the retinaculum extensorium tibiotarsi (dtRET) is prominent and adjacent to the pons supratendineus; 3) the lateral margin of the sulcus extensorius proximal to the pons supratendineus is rounded, not with a sharp crest; 4) the medial attachment point for the retinaculum m. fibularis (mtRMF) laterad of the sulcus extensorius is poorly marked; 5) the lateral attachment for the retinaculum m. fibularis (ltRMF) is on the lateral facies and is aligned anterocaudally rather than parallel to the shaft; 6) a small (not large) foramen penetrates the corpus cranially close to the proximal margin of the condylus lateralis; 7) the distal width across the condyles is narrower caudally than cranially; 8) the depth of the condylus medialis is greater than the distal condylar width; and 9) the epicondylaris medialis is prominent and visible in cranial view. The size of NMNZ S.47666 from Agakauitai Island, Gambier Group, is intermediate between that of the two tibiotarsi of Bountyphaps obsoleta described by Worthy and Wragg (2008) from Henderson Island and greater than those of Alopecoenas (=Gallicolumba) leonpascoi from that island (DW = 7.5-7.8 mm; Worthy and Wragg, 2003). Note, Alopecoenas includes taxa in the Central and Eastern Pacific formerly listed in Gallicolumba, so extinct species erected in this genus and from this region are hereafter placed in Alopecoenas. Tibiotarsi of Alopecoenas nui differ with a markedly prominent mtRMF (4) forming a crest up the lateral side of the sulcus extensorius just proximal to the pons supratendineus; a markedly laterally prominent ltRMF (5) forming a bulge in the lateral margin in cranial aspect and in lacking a prominent epicondylus medialis (8), in addition to their smaller size.
The dR ulna (KAM1-B3TP1-V-3A-B) from Layer V, Kitchen Cave, is referred to Bountyphaps sp. cf. B. obsoleta because it differs from other likely candidate species as follows: from species of Ducula, by the more widely separated papilla remiges; from species of Ptilinopus, by greater size than all except P. magnificens of Australia; and from most species of Alopecoenas by larger size. Alopecoenas leonpascoi of nearby Henderson Island (Worthy and Wragg, 2003), was one of the larger species in this genus, and had a much smaller and slenderer ulna (shaft width of 2.5-2.6 mm, vs 3.3 mm). Larger species than A. leonpascoi are known, notably A. nui from the Marquesas (Steadman, 1992), and provisionally from the Cook Islands (Steadman, 1997), but available descriptions do not include ulnae measurements. However, the size A. nui may be assessed from the recorded distal width measurements for tibiotarsi (7.6-8.4 mm), which do not differ greatly from those for A. leonpascoi (7.5-7.8 mm; Worthy and Wragg, 2003). Given the ulna from Kitchen Cave is much larger than those of A. leonpascoi (maximum DW = 4.6-4.9 and SW = 2.5-2.6 mm; Worthy and Wragg, 2003), it is unlikely to be from A. nui.
Three other fragmentary columbid bones derive from among burnt bone material from layer VI (KAM1-B3TP1-VI-4A-F). The ulna lacks either end, but the rebuilt shaft section distally overlaps part of the specimen KAM1-B3TP1-V-3A-B and is very similar in size and morphology. It shows that overall the ulna is slenderer than those of species of Ducula. The associated shaft of a tibiotarsus is smaller than the specimen referred to Ducula from Onemea and similar to NMNZ S.47666 referred to Bountyphaps from Nenega-Iti. The shaft of the left tarsometatarsus differs greatly from those of spe-FIGURE 2. The distal right tibiotarsus NMNZ S.47666 from Nenega-Iti that is referred to Bountyphaps obsoleta, in cranial (1), medial (2), caudal (3) and lateral (4) views. Abbreviations: dtRET, distal attachment of the retinaculum extensorium tibiotarsi; lc, condylus lateralis; ltRMF, lateral attachment of the retinaculum musculus fibularis; mc, condylus medialis; ptRET, proximal attachment of the retinaculum extensorium tibiotarsi. Scale bar equals 10 mm. 8 cies of Ducula by having an elongated mid-section. It is more like those of Didunculus placopedetes, e.g., L tarsometatarsus, Australian Museum AM138761, in the arrangement of the metatarsal facet and the cristae plantares medialis et lateralis, although the metatarsal facet is medially-prominent in dorsal view (not so in D. placopedetes) and the medial crista on the dorsal facies is farther from the medial margin. An elongate shaft also characterises species of Alopecoenas and the Kamaka Island specimen is within the size range of Alopecoenas nui (Marquesas), see Steadman (1992), but is larger than Alopecoenas leonpascoi (Pitcairn Group), which has a shaft width of 3.6-3.7 mm (Worthy and Wragg, 2003). However, Bountyphaps obsoleta (Pitcairn Group) is larger than A. leonpascoi and of similar size to A. nui and is more similar to species of Didunculus than other taxa (Worthy and Wragg, 2008), so while a tarsometatarsus is unknown for B. obsoleta, it predictably would be elongate like those of species of Didunculus. Moreover, while this is only a shaft fragment it has cristae-like dorsal lineae intermusculari at the level of the fossa metatarsi I, with the medial line enclosing a shallow groove between it and the facet in that fossa, which is strongly developed and protrudes medial to the shaft. In both A. leonpascoi and in A. stairi, the dorsal lineae intermusculari are much weaker and the facet in fossa metatarsi I barely projects medially (Worthy and Wragg, 2003). Given the tibiotarsus and ulna can both be referred to Bountyphaps with some confidence and tentatively to B. obsoleta from Henderson Island some 540 km distant, we consider it most parsimonious to refer the tarsometatarsus from the same site to the same taxon. We think it less likely that two relatively similar taxa would coexist in the Gambier Group, as a referral of the tarsometatarsus to Alopecoenas nui, otherwise known from 1500 km distant in the Marquesas would infer. Steadman and Justice (1998), repeated in Steadman (2006), referred a humeral end of a coracoid and a shaft of a tibiotarsus from Kamaka Island to Alopecoenas nui, which taxon was originally described from the Marquesas, but this was before A. leonpascoi from the Pitcairn Group was known (Worthy and Wragg, 2003). This latter species, while slightly smaller than A. nui, is also relatively large for the genus and attests to a diversity of big species of Alopecoenas across the Central-Eastern Pacific. Moreover, Bountyphaps obsoleta, a similarly large taxon, also from the Pitcairn Group, but with affinities to the long-legged Didunculus-group (Worthy and Wragg, 2008), was also then unknown, and so both Alopecoenas and Bountyphaps, or close relatives, could be expected in the Gambier Group, which is the nearest significant land to Henderson Island. The measurements in Steadman and Justice (1998) do not distinguish the Kamaka Island specimens from either B. obsoleta or A. leonpascoi, and these authors did not figure them. Descriptions were limited to a statement that they do not differ from those of A. nui and some observations of muscular linea on the tibiotarsus shaft, which in-so-far as they can be compared, match what is seen on the bone referred above to B. obsoleta from Nenega-Iti. Given, the most diagnostic columbid bone from Kamaka Island from one of these taxa that we report herein is the distal tibiotarsus, and it does not differ from that of B. obsoleta, we consider the bones Steadman and Justice (1998) reported are most likely of this taxon. Even if they were truly a species of Alopecoenas, then it is more likely that they would be from A. leonpascoi, given the much closer proximity (540 versus 1500 km) of its type locality on Henderson Island to the Gambier Group. Until, the specimens from Kamaka Island that Steadman and Justice (1998) referred to A. nui are compared with B. obsoleta and A. leonpascoi, their identification as being referrable to the Marquesan species A. nui must be considered doubtful.
Genus DUCULA Hodgson, 1836 The following specimens are referred to a species of Ducula because they have the following diagnostic features (Worthy, 2001;Wragg and Worthy, 2006;Worthy and Wragg, 2008). Tarsometatarsus: 1) has similar proportions to other members of the genus; 2) the cotyla medialis in medial view is projected dorsally; 3) the medial foramen of the foramina vascularia proximalia is elongate and much larger than its lateral equivalent; 4) the foramina vascularia proximalia are widely separated by a low ridge and lie in a sulcus bound by prominent ridges; 5) the foramen vasculare proximale medialis lies close (less than the foramen width) to the medial edge of the shaft; 6) the tuberositas m. tibialis cranialis is distal to the foramen vasculare proximale medialis in the sulcus extensorius and so is close to the medial margin; 7) the lateral profile of the shaft leading to trochlea metatarsi IV is slightly concave. Tibiotarsus: 8) 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 the medial condyle; 9) the distal attachment point for the retinaculum extensorium tibiotarsi (dtRET) is a marked prominence on the lateral side of the sulcus extensorius proximal to the pons supratendineus; 10) the lateral margin of the sulcus extensorius proximal to the pons supratendineus is bound by a sharp crest; 11) the medial attachment point for the retinaculum m. fibularis (mtRMF) laterad of the sulcus extensorius is poorly marked; 12) the lateral attachment of the retinaculum m. fibularis (ltRMF) is on the lateral facies and is aligned parallel to the shaft; 13) it lacks a foramen penetrating the corpus cranially close to the proximal margin of the condylus lateralis; 14) the distal width across the condyles is about the same caudally and cranially; 15) the depth of the condylus medialis is about equal to the distal condylar width.
The tibiotarsus and tarsometatarsus differ from those of known species of Ducula, so they are described as a new taxon. The remaining bones are referred to the same new species because they are of appropriate size and were found in close proximity to the above elements and no other similarly large columbid species was represented in the site.

Diagnosis
A species of Ducula with tibiotarsi and tarsometatarsi smaller than those of the extinct Ducula lakeba of Fiji, D. david of Uvea, D. harrisoni of Henderson Island and the extant D. goliath of New Caledonia and D. galeata of the Marquesas, but larger than all other species east of the Solomon Islands (Worthy, 2001;Wragg and Worthy, 2006). The tarsometatarsus is robust with similar proportions to that of D. david from Uvea (Balouet and Olson, 1987), as defined by maximum shaft width across the articular facet in fossa metatarsi I as a proportion of length, and is more robust than those of other large species such as D. galeata, D. harrisoni and D. lakeba (Worthy, 2001;Worthy and Wragg, 2008). The fossa parahypotarsalis medialis separated from the fossa metatarsi I. Dorsal facies with very well marked lineae intermusculari, one medially, one laterally and one intermediate.

Etymology
The species is named after the late Tihoni Reasin, who was the owner of Kamaka Island. Tihoni, as a 14-year old, worked with Roger Green in the first excavation of Kitchen Cave. He then greatly assisted PV Kirch and his team in all of their field trips to Mangareva, and especially during the 2012 and 2014 re-excavations at Kitchen Cave, when he hosted them on Kamaka.

Description and Comparisons
In addition to the diagnostic features listed above, we note other features that distinguish Ducula tihonireasini n. sp. from its geographically closest congener, D. harrisoni of Henderson Island, which has larger and more gracile tarsometatarsi. The dorsal lineae intermusculari form elevated cristae along their length and are much more prominent than those on D. harrisoni, see Wragg and Worthy (2006). The one on the medial margin connects the tuberositas m. tibialis cranialis and trochlea metatarsi II. The lateral linea, in dorsal aspect, forms a straight crest extending along the margin distal to the lateral foramen vasculare proximale onto the dorsal surface of trochlea metatarsi IV where it diverges from the shaft. The middle linea commences by defining the lateral margin of the lateral foramen vasculare proximale, then extends distally as the dorsal crest of the dorsal facies to pass on the medial side of the foramen vasculare distale. All three lineae are much more weakly marked on the Henderson D. harrisoni. Plantarly, the crista plantaris lateralis in D. tihonireasini is more strongly developed. Ducula harrisoni further differs from D. tihonireasini by greater separation of fossa parahypotarsalis medialis from fossa metatarsi I. The fossa metatarsi I is deeper in Ducula tihonireasini and includes a discrete sulcus just distal to the facet for articulation of the os metatarsale. Also, this facet is relatively larger and extends beyond the medial shaft margin to a greater extent. The only species with a similarly stout shaft is D. david, however, in this species the fossa parahy-potarsalis medialis is relatively larger and distally abuts the fossa metatarsi I (Wragg and Worthy, 2006).
Ducula galeata has a far more slender tarsometatarsus, with NMNZ O.26971 having greater length and proximal width values, but substantially narrower shaft width values as follows (those of D. tihonireasini in brackets for comparison): length from proximal end to foramen vasculare distale 34.6 mm (33.0), length to distal side of the metatarsal facet 26.7 mm (24.1), length from posterior edge cotyla medialis to distal end of medial prominence of fossa metatarsi 1 25.0 mm (18.0), proximal width 10.8 (9.6 mm) mm, least shaft width distal to metatarsal facet 3.6 mm (4.6 mm), width at metatarsal facet 4.1 mm (5.3 mm). The tibiotarsus of D. galeata has greater distal width (10.2 mm) but a similar shaft width (4.4 mm), consistent with D. tihonireasini having a relatively stout shaft as the measurements of the tarsometatarsus would predict. However, but D. tihonireasini differs further with much more robust attachment points for the retinaculum extensorium tibiotarsi and thus a deeper sulcus extensorius.

Comments
Within the clade of frugivorous pigeons, there were in the prehuman period very often three sizeclasses in an archipelago, a small Ptilinopus fruit dove, and medium-and large-sized species of imperial pigeons in the genus Ducula, e.g., D. pacifica and D. goliath. However, recent phylogenetic analyses of molecular data have shown that the larger species of Ducula do not form a clade and have evolved repeatedly from smaller relatives . The size classes shown by fruit pigeons doubtless reflect niche segregation based on the size of fruit that can be swallowed (Meehan et al., 2002). The only surviving large species of Ducula are D. goliath on New Caledonia and D. galeata in the Marquesas. However, in the huge intervening area between where these taxa live, there once occurred numerous other large, now extinct, species or populations that could disperse fruit larger than 28 mm in diameter, which is the maximum that D. pacifica can eat (Meehan et al., 2002;Steadman, 2006). These include Ducula sp. cf. D. goliath on Efate in Vanuatu (Worthy et al., 2015), an undescribed Ducula sp. on Viti Levu and D. lakeba in the Lau Group, Fiji (Worthy, 2001), an undescribed species from Rapa Island in the Austral Group (Tennyson and Anderson, 2012), D. david on Uvea in Wallis and Futuna (Balouet and Olson, 1987), an undescribed Ducula sp. on 12 several islands in Tonga (Steadman, 1989b(Steadman, , 1993(Steadman, [as D. david], 1995(Steadman, , 1997(Steadman, , 2006, extirpated populations referred to D. galeata on Mangaia in the Cook Islands and Huahine in the Society Islands (Steadman, 1989a(Steadman, , b, 1995(Steadman, , 1997(Steadman, , 2006, and D. harrisoni on Henderson Island (Wragg and Worthy, 2006). The discovery here of another large species of Ducula in the Gambier Group reinforces the idea that there has been parallel evolution of large forms on many of the islands or archipelagos of the Pacific (Worthy et al., 2015). Furthermore, given the presence of distinct large species of Ducula on Henderson Island and in the Gambier Group, then the identification of fossils from the Society and Cook Islands as D. galeata (extant only in the Marquesas) may need revisiting, as their identification as a similarly large but distinct species of Ducula may be more likely.

Comments
A mere three fragmentary specimens attest to the former presence of Ptilinopus doves in the Gambier Group. The dR tmt preserves only the area distal to the facet in the fossa metatarsi I, which with a length of 10.2 mm is of a bird a bit larger than P. regina. It also lacks all the plantar part of trochlea metatarsi II and all of trochlea metatarsi IV, but has a least shaft width of 2.3 mm and an estimated distal width of about 5.6 mm. Similarly, the two distal tibiotarsi fragments, which lack the condyles and preserve the pons supratendineus and some shaft proximal to that, indicate a dove a bit larger than P. regina. They are identified as of a species of Ptilinopus by general resemblance to, for example, P. regina, and especially by the locations of the attachment points for the retinaculum extensorium tibiotarsi. The proximal attachment point (ptRET) is prominent and lies far proximal to the condylus medialis. The distal attachment point (dtRET) is a narrow, very elongate and prominent crest, extending from the pons supratendineus proximally along the margin of the sulcus extensorius.
The small columbid Alopecoenas erythroptera, extant in the nearby Tuamotu Archipelago, was possibly present on the Gambier Group in the nineteenth century Cibois, 2012, 2017) and was recorded from Kamaka Island based on a humerus (Steadman and Justice, 1998). The distal width of the tarsometatarsus in this species is 6.9-7.2 mm (Steadman, 1992) so is larger than the specimen recorded here. Furthermore, the Onemea tarsometatarsus is similar to species of Ptilinopus in having the facet in fossa metatarsi I located well proximal to the foramen vasculare distale; the facet lies much closer to the distal end in species of Alopecoenas.
Thibault and Cibois (2012) reported a species of Ptilinopus based on Kirch et al.'s (2010: 75) statement that "David Steadman…. noted the rare presence of 4 bones of pigeon, 3 bones of fruit dove…". The latter are the three specimens reported here. Thibault and Cibois (2012) noted that several visitors recorded a probable fruit dove during the nineteenth and early twentieth centuries, but that no specimen was known to have been collected. Species of Ptilinopus survive in the Tuamotu Archipelago (P. chalcurus, P. coralensis), the Marquesas (P. dupetithouarsii, P. mercierii) and Henderson Island (P. insularis) so a former presence of this genus in the Gambier Group is to be expected. Of these bones, the carpometacarpus is potentially the most diagnostic. It is 29.2 mm long and has a large cranially-directed processus extensorius, whereon the proximal margin is at right angles to the bone axis, except for a slight proximal projection at its tip. It has a large and ventrallyprominent processus pisiformis, the ventral rim of the trochlea carpalis is rather short, terminating distally level with the tip of the processus extensorius, and the processus intermetacarpalis is small and in the proximal half of the spatium intermetacarpalis. The carpometacarpus attributed to Bountyphaps obsoleta by Worthy and Wragg (2008) is longer (33.8 mm), and the ventral rim of the trochlea carpalis is longer, extending distally beyond the processus extensorius. However, it is similar in that the processus extensorius is not directed proximally, the trochlea carpalis lacks a fossa infratrochlearis ventrally, and the processus intermetacarpalis is in a similar location (Worthy and Wragg, 2008, figure 2A). KAM1-B3TP1-VI-16-2A also differs markedly from carpometacarpi of Alopecoenas species, which are characterised by a strongly proximally-directed processus extensorius, and are smaller, even in the large A. leonpascoi (length 21.9-24.2 mm; Worthy and Wragg, 2003). Species of Didunculus are also characterised by a proximally directed processus extensorius, but tend to have a distally short ventral rim of trochlea carpalis (Worthy and Wragg, 2008, figure 2). This carpometacarpus is much too small to be associated with the species of Ducula recorded from Teouma, and too large to be associated with the Ptilinopus bones.
It is possible that KAM1-B3TP1-VI-16-2A, represents a species of Macropygia. Steadman (1992) described the relatively large and extinct cuckoo doves M. arevarevauupa from Huahine, Society Islands, and M. heana from the Marquesas. The latter had carpometacarpi that ranged in length 28.0-29.6 mm, so are of appropriate size for the Kamaka pigeon, but were not described or figured by Steadman (1992). However, M. amboinensis, e.g., AM O.70775, differs from the fossil with a more elongate ventral rim of the trochlea carpalis, a more proximally directed processus extensorius and the os metacarpale minus extending distal to os metacarpale majus (equal in the fossil). In summary, this carpometacarpus has features that preclude its attribution to Bountyphaps and it is of an appropriate size to be a species of Macropygia. Whatever its relationships, it represents a fourth species of pigeon for the Gambier Group.
Of the remaining bones, the scapula is of appropriate size to be associated with the bones identified as Bountyphaps sp. cf. B. obsoleta but is not so identified because columbid scapulae are poorly diagnostic. The humeral shaft is of appropriate size to be associated with the carpometacarpus, but is too incomplete to inform on relationships.

Measurements
Summary statistics for measurements (mm) of the Pseudobulweria bones are compared to those of individuals of other procellariids in Table 1

Comments
The abundant bones listed here represent a small species of Pseudobulweria, one that is slightly smaller than Pterodroma heraldica or similar to P. leucoptera. This taxon was first identified by Worthy and Tennyson (2004) and is much smaller than P. rostrata, precluding their being small specimens of that taxon (contra Thibault and Cibois, 2017). In terms of proportions, this Gambier species of Pseudobulweria compares to the similar-sized and sympatric Pterodroma leucoptera (SAM B31271a) as follows: the premaxilla is of similar length; the coracoids are slightly smaller overall; the ulnae and humeri are slenderer, but slightly longer; the tibiotarsi are slightly longer, but stouter, especially distally; and the tarsometatarsi are slenderer and longer.
The Gambier taxon conforms with Pseudobulweria rostrata and differs from species of Pterodroma as follows. Cranium: relatively narrower in dorsal view at both lacrymals and processus postorbitales, but with a relatively wider nasofrontal hinge; the preorbital region at the lacrymals is craniocaudally shorter and the preorbital lacrymal processes more directed caudally; the fossae temporales are more extensive both craniocaudally and medially, meeting on the midline; the nares are more widely separated from the nasofrontal hinge on the premaxilla at a distance of about 2/3 hinge width (~1/2 in Pterodroma); and the processus nasalis of the premaxilla is not evident at or anterior to hinge (lateral edges well-marked by lines in Pterodroma). Humerus: more elongate and the impression for the brachialis anticus within the fossa brachialis is well defined distally and near circular (not defined well distally and oval in Pterodroma). Ulna: more elongate and the tip of the tuberculum carpale projects somewhat distally enclosing a notch distally (markedly so in P. rostrata; projects somewhat proximally in Pterodroma).
Carpometacarpus: the processus pisiformis is much larger. Coracoid: the processus acrocoracoideus is much deeper dorsoventrally and depth widens towards the tip, whereas depth at along the processus is similar in Pterodroma. Tarsometatarsus: much more elongate relative to both humeri and coracoids and more strongly ridged dorsally, especially along the lateral side enclosing a much deeper sulcus extensorius. Lastly, Pseudobulweria has a major structural difference of the hypotarsus, where the middle hypotarsal ridge (crista lateralis flexoris digitorum longus, Mayr, 2016), which is prominent in Pterodroma, is markedly reduced. This results in the lateral sulcus for the tendon of musculus flexor hallucis longus (fhl) being merged with that medially for the sulcus for the tendon of musculus flexor digitorum longus (fdl) as a single sulcus. Bounding this laterally, the crista lateralis flexoris hallucis longus is much more robust and, plantarly, is both laterally and medially expanded to form a broad, flat, crista with a shallow sulcus for the tendon of musculus flexor perforatus digiti 2 on its plantar side.
Three species of Pseudobulweria occur in the Pacific, Tahiti Petrel P. rostrata, Beck's Petrel P. becki, and Fiji Petrel P. macgillivrayi, one in the Indian Ocean Mascarene Petrel P. aterrima and an 16 extinct taxon P. rupinarum is known from St Helena Island in the Atlantic Ocean (see Gangloff et al., 2012;Dickinson and Remsen, 2013). The bones recorded here represent a much smaller species than P. rostrata (culmen length 33.1-38.2 mm, tarsus length 43.3-51.0 mm; Villard et al., 2006), which is the only extant representative of this genus known from the Gambier Group . Based on a tarsometatarsus length of 35.6-36.7 mm (Table 1) and a premaxilla length c. 30.0 mm (NMNZ S.47669) the species formerly in the Gambier Group was of similar size to the remaining three extant species of Pseudobulweria. Of the Pacific taxa, P. macgillivrayi breeding on Gau Island, Fiji (Watling and Lewanavanua, 1985;Priddel et al., 2008;Shirihai et al., 2009), is geographically the closest breeding species, and is of appropriate size with a tarsus length of 36-38 mm and an unfeathered bill length (slightly less than premaxilla length) of 25.0-25.7 mm (Shirihai et al., 2009). Steadman and Justice (1998) identified an ulna 78 mm long as Bulweria sp. cf. B. fallax, however this bone was not compared to those of any species of Pseudobulweria. Among the ulnae, we attribute to Pseudobulweria sp. are two with complete length (80, 83 mm; Table 1), which are not the smallest in the sample, so the bone attributed to Bulweria could be the same taxon, as suggested by Worthy and Tennyson (2004). This suggestion is supported by the observation that the ulnae we refer to Pseudobulweria have the main features used by Steadman and Justice (1998)   processus cotylaris dorsalis is smaller/less projecting in the ulnae identified as Pseudobulweria sp. than in species of Puffinus, but it is similar in size and projection to, for example, Pterodroma leucoptera, and in all compared taxa, the distal margin of the processus is at right angles to the shaft in dorsal view.

Material
Family OCEANITIDAE Salvin, 1896Genus NESOFREGETTA Mathews, 1912 Nesofregetta fuliginosa (Gmelin, 1789) Nesofregetta fuliginosa has a widespread breeding distribution in Eastern Polynesia on islands free from predators, including the Gambier Group . Metrics for these specimens are shown in Table 3.
Order PELECANIFORMES Sharpe, 1891 Family ARDEIDAE Leach, 1820 Genus EGRETTA T. Forster, 1817 Egretta sacra (Gmelin, 1789) This species is widespread in the Pacific, with birds smaller in Eastern Polynesia than in the West . It is a common breeding species in the Tuamotu Archipelago, but in the Gambier Group, breeding is limited to a few pairs .
Family FREGATIDAE Degland & Gerbe, 1867 Genus FREGATA Lacépède, 1799 Fregata ariel (Gray, 1845) This species breeds in widespread localities in Eastern Polynesia including the southern part of the Tuamotu Archipelago, but is only a visitor to the Gambier Group . This species breeds in widespread localities in Eastern Polynesia including the Gambier Group .
Order CHARADRIIFORMES Huxley, 1867 Family LARIDAE Rafinesque, 1815 Genus GYGIS Wagler, 1832 Gygis alba (Sparrman, 1786) This widespread species breeds in most part of Eastern Polynesia, the Gambier Group included . Laridae magn. Procelsterna cerulea (Bennett, 1840), These bones are too fragmentary for a certain taxonomic assignment from morphology, but they are most similar to bones of terns and based on size are likely to be from Procelsterna cerulea, which is widespread in the Tuamotu Archipelago . However, the Grey Noddy, P. albivitta, has a more southerly breeding distribution that includes the Austral and Pitcairn groups (Dickinson and Remsen, 2013) and, in the Gambier Group, birds have a plumage intermediate between the two taxa , precluding a certain specific assignment, if these taxa are indeed distinct.

Summary
The NISP and MNI generated by taxa for each stratigraphic unit are given in Appendix 1 for the faunas from the three sites from the Gambier Group reported here, Onemea (Taravai Is.), Nenega-Iti Site (Agakauitai Is.) and Kitchen Cave (Kamaka Is.). Table 4 provides a summary of the total NISP and MNI for each taxon, calculated by totalling the MNI from all stratigraphic units by site. A total of 647 bones from 192 individuals were identified to family-level or lower, and were distributed by site as follows: Onemea 419 bones, MNI of 102; Nenega-Iti Site 139 bones, MNI of 44; Kitchen Cave Site 89 bones MNI of 46. These minimally represent 15 species of seabirds and six of land birds, one being the prehistorically introduced junglefowl (Gallus gallus). With the addition of the previously identified bones (Table 5), the proportions of seabirds to land birds and of the various families was calculated and shown in Figure 4. This reveals that seabirds dominate the faunas and among those, procellariids predominate. Land bird faunas are too small for discernment of meaningful trends, but columbids dominate the main assemblages.

DISCUSSION
The new investigations reported here considerably add to the known prehistoric avifaunal record for the Gambier Group, which until now was based on 215 identified bones (Steadman and Justice, 1998;Steadman, 2006). Our new data are compiled in Table 5 with those of Steadman and Justice (1998), and the modern and historic record of birds from the Gambier Group , to estimate the former diversity of breeding taxa.
We report minimally 14 species of seabird in the prehistoric record of the Gambier Group (Table  5), including three (Pseudobulweria sp., and Pterodroma magn. P. heraldica and Pt. magn. P. leucoptera) that have not been previously recorded in the archaeological faunas, although Steadman and Justice (1998) noted indeterminate small to large species of Pterodroma. Of these oceanic birds, minimally seven are procellariids ( Figure 5), with the proviso that we consider the previous records of Bulweria sp. cf. B. fallax and Puffinus lherminieri to be equivalent to Pseudobulweria sp. indet. and Puffinus bailloni respectively. However, we reiterate that because of the cryptic nature of procellariids, more than one species may be represented by our taxa that reflect size classes, e.g., Pterodroma magn. leucoptera and P. magn. heraldica. For the latter, Pterodroma ultima, P. neglecta and P. heraldica all breed in the Gambier Group, although others, as noted in the Introduction (above), are probable visitors . In order to conservatively establish the diversity of former breeding seabirds, we assume that the taxon Pterodroma magn. leucoptera, which was relatively abundant in the fauna from Onemea (Taravai), represents one breeding species, although several similar-sized small Pterodroma species certainly feed seasonally in the oceans about the Gambier Group (see Introduction). This species is likely to be Pterodroma brevipes, or a closely related taxon, as this species has the closest breeding populations today .
We do not accept the interpretation that the record of Puffinus tenuirostris reflects an extirpated population (Steadman, 2006: 237), as this species breeds in the millions in cool-temperate climates about Australia and migrates to the northern Pacific annually, passing on their return through eastern Polynesia (Marchant and Higgins, 1993), as noted by Steadman and Justice (1998). It is therefore likely that the few birds represented, if correctly identified, are from birds caught when attracted to the colonies of resident procellariids as has been regularly reported (e.g., Warham, 1990;Imber et al., 1991).
To establish the likely extent of the actual diversity of breeding seabirds, we have added to Table 5 other taxa known to breed in the Gambier Group . This results in the addition of three sulids and the tern Anous minutus. Steadman (2006) listed Pterodroma lessoni from the Gambier Group, but this species is a non-breeding visitor and so we exclude it from the list of resident seabirds. Similarly, all other procellariiform non-breeding visitors to Eastern Polynesian waters near the Gambier Group, e.g., Pelagodroma marina, Fregetta grallaria, Macronectes giganteus, Pterodroma cookii, Pt. atrata, Pt. alba, Pt. externa, Pt. cervicalis, Pt. macroptera, Procellaria cinerea, Pr. aequinoctialis, Pr. parkin-soni, Ardenna grisea, A. carneipes, [see Thibault and Cibois (2017)] are not listed. All might be expected to contribute rare specimens to an avifauna in the region. In summary, the 19 oceanic seabird taxa listed as breeding in Table 5 equate minimally to 21 species likely to have been breeding in the Gambier Group.
There are perhaps minimally a further 12 species of land birds in the original breeding avifauna of the Gambier Group. Dominating the prehistoric record are rare bones of five species of columbids. Two of these are extinct and newly recorded for the Group, an imperial pigeon Ducula tihonireasini n. sp. and Bountyphaps sp. cf. B. obsoleta known originally from Henderson Island. The new species of Ducula is most likely a local endemic species given that it differs from congeneric taxa on Henderson Island and in the Marquesas (Worthy and Gygis alba B --14+7 (9+4) -66 (16) 14+73 (9+20) 1. We consider it most likely that this specimen identified by Steadman and Justice (1998) belongs to the taxon identified here as Pseudobulweria sp. indet. 2. The bones referred by Steadman (2006) to Puffinus lherminieri were identified before separation of that Atlantic Ocean taxon from the Pacific birds, so they would now be listed in our taxon Puffinus magn. P. bailloni. Puffinus bailloni is a common breeding bird in the Gambier Group but the similar sized P. auricularis myrtae is a likely visitor to the area and would not be distinguished on bones. 3. We consider it more likely (as discussed above) that the bones referred to Alopecoenas (=Gallicolumba) nui by Steadman and Justice (1998) from Kamaka Island belong to the same taxon as those we refer to Bountyphaps sp. cf. obsoleta, so they are included here.   Wragg, 2008). However, the same may not be the case for Bountyphaps, under which taxon we list the specimens identified as Gallicolumba nui by Steadman and Justice (1998), see above in species accounts. Caution is required in interpreting the presence of Bountyphaps in sites on Kamaka and Agakauitai as representing an autochthonous population for two reasons. Firstly, these sites are not as old Kirch et al., 2010) as the Onemea site on Taravai, where Bountyphaps was not found despite a large sample of bird bones. Secondly, the early Polynesian colonisers were adept at transporting birds, having introduced Gallus to the Gambier Group in the earliest period of colonisation (Green and Weisler, 2004) and there is ample evidence of various commodities being transported back and forth from the Pitcairn Group around AD 1000 (Green and Weisler, 2002). This includes basalt tools with a Pitcairn source found in Aukena Rockshelter (GA-1) and on Agakauitai Island (Green and Weisler, 2002). This evidence of return voyaging from the Pitcairn Group makes it at least possible that the Bountyp-haps bones may represent birds imported from Henderson Island. A further three smaller columbids have been extirpated from the Gambier Group but survive elsewhere: a ground dove Alopecoenas erythropterus, which possibly was reported historically (Thibault and Cibois, 2017), a fruit dove Ptilinopus sp. indet. and a species that perhaps was a cuckoo dove Macropygia sp.

Modern Status Prehistoric Records
The columbids are all rare in the fauna and occur only in the oldest layers ( Figure 5), so it is highly likely that other terrestrial taxa have escaped detection due to the relatively small sample sizes from the earliest stratigraphic contexts. The only other native land bird in the prehistoric record is the heron Egretta sacra, which still is a breeding species in the Gambier Group. To these prehistorically known land birds, a further six presumed breeding resident species only recorded historically (H -Table 5), from the 18 th to early 20 th century) can be added (a rail, a shorebird -Prosobonia, a kingfisher and three passerines) for a total of 12 breeding species. It is notable that there are no fossil rails in the prehistoric record of the Gam-FIGURE 4. Relative proportions of seabirds and land birds, and of the constituent families for each group, for the Gambier Group as a whole (left) and individual islands/sites. Data is based on the 647 bones reported herein plus the 215 specimens previously reported as compiled in Table 5. bier Group, despite an historic record of spotless crake (Zapornia tabuensis) in the Gambier Group, and of this and other crakes having a widespread extant and prehistoric presence in Eastern Polynesia (Steadman, 2006;Thibault and Cibois, 2017). Similarly, it is surprising that no parrots have been found, despite the present and former abundance of several species of Vini lorikeet in the Tuamotu Archipelago and the Marquesas and of V. stepheni on Henderson in the Pitcairn Group (Steadman, 2006;Thibault and Cibois, 2017). Alongside these 12 breeding land birds, we list four migratory charadriid and scolopacid shorebirds, given that they live and feed on land in the coastal areas, and the migrant cuckoo (Urodynamis) known from contemporary observations (Table 5), although Numenius was recorded in the prehistoric record by Steadman and Justice (1998).
In summary, there were minimally 32 breeding species (20 oceanic seabirds, 12 land birds) in the pre-human avifauna of the Gambier Group. With the addition of five regular migrants (a cuckoo and four shorebirds), a total of minimally 37 species contributed to the resident avifauna in the Gambier Group. Of these, at least seven species, a seabird (a Pseudobulweria sp.), three columbids (one conservatively identified as Bountyphaps obsoleta, first described from Henderson Island (Worthy and Wragg, 2008), the new species Ducula tihonireasini described herein, and an undetermined taxon that possibly is a species of Macropygia) and three other land birds, are extinct. Five others have had their Gambier breeding populations extirpated (one seabird -Pterodroma magn. Pt. leucoptera, Prosobonia parvirostris, a rail, and two columbids). Of these columbids, the Ptilinopus sp. probably represents an extirpated population of Ptilinopus coralensis (Atoll Fruit Dove), which is widespread in the Tuamotu Archipelago; it has been recorded as a vagrant in the Gambier Group . Similarly, Alopecoenas erythropterus, while rare now, historically had a widespread breeding range in the Tuamotu Archipelago and in the Society Group . To these taxa can be added Gallus gallus, whose bones were rare in all sites but were found in the deeper layers, corroborating the observations of Steadman and Justice (1998) and indicating an early Polynesian introduction to the Gambier Group. However, this species was extirpated prior to European contact (Green and Weisler, 2004).
The size of our Gambier bird bone sample is small compared to other archaeological avifaunal assemblages, e.g., 42,213 bird bones from Hen-FIGURE 5. The recorded presence (black) or inferred presence but no data for (grey) of selected taxa through the archaeological record to the present in the Gambier Group showing how some taxa survived only into the fourteenth and fifteenth centuries.
derson Island (Wragg, 1995), so it probably provides a still limited view of the past avifauna. Nevertheless, it suffices to show that the composition of original avifauna, especially of the seabirds, differed between islands in the Gambier Group, as it does currently (Waugh et al., 2013). For instance, on the adjacent Taravai and Agakauitai islands, Pterodroma magn. Pt. heraldica and Pseudobulweria sp. were common, but both were respectively, rare or absent on Kamaka Island. In contrast, Nesofregetta fuliginosa was abundant on Kamaka, while represented by just one bone on Taravai and none on Agakauitai. This pattern almost certainly reflects local breeding populations on these islands, and so colonies of a mediumsized petrel and a Pseudobulweria sp. were almost certainly on the adjacent islands on Taravai and Agakauitai, but not on Kamaka, a small species of Pterodroma only bred on Taravai, and N. fuliginosa only had a colony on Kamaka. In contrast, three species of shearwater, including a small species that was most likely P. bailloni, Puffinus nativitatis, and Ardenna pacifica probably bred on all three islands. The numbers of terrestrial birds are probably too small to determine whether there was any regionalisation of species within the Gambier Group. The observation that Ducula bones were only found on Taravai and those of Bountyphaps mainly on Kamaka is suggestive that these two islands had discrete columbid faunas. However, a Bountyphaps bone was also found on Agakauitai, which is very close to Taravai, thus it is most unlikely that Taravai really lacked Bountyphaps, and the apparent differences probably relate to the small sample sizes available of land birds.
Overall, the Gambier Group avifauna is most similar to that from prehistoric Henderson Island (Wragg, 1995;Steadman, 2006). Seabirds dominate the assemblages and land birds are relatively rare (2.3 -11.8% NISP; Steadman, 2006), with the higher values deriving from the non-archaeological assemblages reported by Wragg (1995). These higher numbers of land birds include Porzana atra as 4.4% of NISP, and four species of pigeon and one Vini parrot, and support the contention that the archaeological sample from the earliest humancontact layers for the Gambier Group is as yet too small to reveal the rail fauna and the relative frequencies of the represented columbids. The prehistoric avifaunas from the Marquesas are also similar to those from the Gambier Group in the rel-ative proportions of seabirds and their species diversity (Steadman, 2006). However, the land bird fauna is notably more diverse, with three rallids in two genera (Gallirallus, Zapornia [as Porzana]), six columbids in four genera, and three species of Vini parrots (Steadman, 2006). Heading west from the Gambier Group, the land bird faunas become increasingly diverse when large samples are available, with the Society Islands having three genera of rails among 25 species of land birds, Mangaia Island in the Cook Islands three genera and six species of rails among 27 land bird species (Steadman, 2006). Therefore, it is to either the Marquesas or Henderson Island that we can turn to estimate what is likely to be found in the Gambier Group when further archaeological excavations expand the recovery of larger and first contact avifaunas. Minimally one, but probably two rails and at least one Vini parrot arguably await discovery, and more bones will be required to better elucidate the columbids formerly present.

APPENDIX 1
Distribution of bird bones by Layer in the three archaeological sites excavated by P. V. Kirch et al. in the Gambier Group. Data shows NISP and MNI in brackets. X: unknown layer. Site total is the sum of all layers.  (2) 15(3) 20(4) 33(4) 2(1)