Distribution of Brown Teal

Brown teal bones representing at least 641 individuals are recorded from 73 fossil sites (Figure 1, 2).  The given frequency data is an under-estimate as data for three significant sites (Honeycomb Hill Cave complex, Megamania Cave, Poukawa N141/1-2) were not available. As these data are mainly based on literature records, there will likely be other unpublished records available from museum collections, but those given reveal the pattern of distribution and relative frequency of Brown Teal in relation to other anatids. The distribution of archaeological sites with Brown Teal remains is shown in Figure 3.

Northland dunes

The Northland dunes that have revealed most fossil deposits in the Far North of New Zealand include the dune fields of Doubtless Bay (Tokerau Beach) and others on the Karikari Peninsula, and those along the east coast of Aupouri Peninsula to North Cape and around to Cape Maria Van Diemen. All fossil deposits are in palaeosols developed under terrestrial vegetation – none are swamp or lake deposits. The data here are based on Millener (1981) who provided the latest summaries for each site. A considerable amount of more recent collecting by Brian Gill (Auckland Institute and Museum), Alan Tennyson (Museum of New Zealand Te Papa Tongarewa [MNZ]), and Worthy has occurred but summary data are not yet available. Anatids are a minor component of these faunas as shown by the total minimum number of individuals (MNI) of just 27. However, Brown Teal was the most abundant anatid species, and is likely to be underscored as the records of grey teal probably pertain to Brown Teal. 

 The palaeovegetation of the dunes in the Far North were reconstructed by Atkinson & Millener (1990) as a mosaic of coastal broadleaf/podocarp forest, coastal scrub, and dune grasslands.  Most dune sites were not directly associated with wetlands, though small streams flowed through some area, eg. the Tokerau Beach dunes, and swamps and small lakes backed onto some areas e.g. Cape Maria van Diemen. Atkinson & Millener (1990) listed Brown Teal and Finsch’s ducks as aquatic insectivores that were forest inhabitants. As Brown Teal was 3-4 times more abundant than typical aquatic ducks (grey duck, scaup) the suggestion that it was of more than incidental occurrence in these deposits, is supported.

Waitomo karst

The Waitomo karst is in the area between the Awakino and Waikato Rivers west of the Waipa River centred on Waitomo Caves in the west of the North Island. The karst landscape is developed mainly between the altitudes of 300 and 500 m asl. Anatids are relatively abundant in fossil sites in the Waitomo karst and Brown Teal is the most abundant species overall. All fossil faunas come from cave deposits, which are often time-averaged (Worthy & Swabey in press). This means, specimens of disparate ages are often grouped as single faunas. As Finsch’s duck was mainly a shrubland inhabitant, most of the Waitomo records for this species may be of Pleistocene age, and so the true frequency of Finsch’s duck in the Waitomo karst during the Holocene may be lower than indicated in Table 1.

 One of the most important sites for Brown Teal fossils in the Waitomo area is F1c Cave (Worthy 1984).  There, Brown Teal were abundant in the upper Layers 2&4. The site is a pitfall trap adjacent to a small (10 x 30 m) flat depression in a broad valley floor. This depression was assumed by Worthy (1984) to have been a swampy and relatively open area that seasonally held water. While Carex sedges and treeferns were on the margins of this ‘wetland’, a podocarp (matai Prumnopitys taxifolia, rimu Dacrydium cupressinum) forest with associated hardwoods like tawa Beilschmiedia tawa formed a tall closed canopy forest all around the site. No streams flow on the surface in the valley around the site, and the nearest is 1-2 km distant.

 While, the presence of Finsch’s duck in the Holocene is verified by its bones in the stratified sequence in F1c Cave (Worthy 1984; Worthy & Swabey in press) the data from F1c cave show changes in relative frequency of Brown Teal and Finsch’s duck over time. In the 1500-2000 ¹⁴C yrs BP Layers 2&4, Brown Teal were three times as abundant as Finsch’s duck, whereas in the 12,000 ¹⁴C yrs BP Layer 8, there were three Finsch’s duck and only one Brown Teal. This faunal change is paralleled by other changes in the compared avifaunas which Worthy & Swabey (in press) related to changes in the vegetation around the site. Regionally, the vegetation was dominated by shrubs in the late glacial, which were rapidly replaced by a closed forest in the earliest part of the Holocene. In the Pleistocene deposits of Gardners Gut Cave (Worthy & Swabey in press), Finsch’s duck dominates the anatid fauna. The presence of Finsch’s duck at F1c in the late Holocene may relate mainly to the presence of the small forest opening that was postulated to have been around the site.

 Atkinson & Millener (1990) reconstructed the palaeovegetation of the Waitomo karst for most of the Holocene as a rimu/tawa forest. Podocarps, mainly rimu with some miro (Prumnopitys ferriginea), and northern rata (Metrosideros robusta) emerged over a tawa canopy. Hinau (Elaeocarpus dentatus) and mangeao (Litsea calicaris) were also common canopy components, with kamahi (Weinmannia racemosa) on steeper slopes. Shrublands and grasslands were absent or very rare in this area during the Holocene, and the only wetlands were small streams.  The incidence of Brown Teal fossils can be interpreted a lot more strongly than that they “may have used vegetated areas beyond stream courses” (Atkinson & Millener 1990). Most fossil sites in the Waitomo karst are of pitfall origin, with none known to have been accumulated by predators. As such, fossils have an origin as a live bird at the cave entrance, and as most sites are not stream submergences, and usually are 10s to 100s of metres from streams, then it must be presupposed that the birds were using forest near these entrances before they were entrapped.

 Hawke’s Bay (excluding Lake Poukawa)

The sites grouped under the umbrella of Hawke’s Bay include coastal dune sites at Ocean Beach and inland rockshelters. The coastal dune sites were probably formerly vegetated in coastal broadleaf forest dominated by kohekohe (Dysoxylum spectabile) and karaka (Corynocarpus laevigatus) and were not associated with wetlands. The faunas in the inland sites were accumulated by avian predators, so the teal could have been taken either on wetlands (streams) or in forest glades. There are very few pitfall sites in which to trap faunas, so a direct comparison with Waitomo is not possible.

 Lake Poukawa.

The fauna from the Holocene deposits of Lake Poukawa, Hawke’s Bay, includes the largest collection of anatid remains known from New Zealand. There are two main and several minor sites at this locality and the fauna of only one (N141/12) has been described (Horn 1983). In Table 1 the values for the named taxon are the total for Layers 1-3 from Horn (1983). However, Horn also listed shoveler (Anas rhynchotis) and blue-billed duck (Oxyura australis). Specimens attributed to the latter are all now considered to be other taxa but mainly scaup (Holdaway et al. 2000). Several bones of the large extinct anatid Scarlett’s pink-eared duck (Malacorhynchus scarletti) were unrecognised as such and were confused with grey duck (pers obs.).  Horn did not state how grey teal was separated from Brown Teal, but it was likely on size, and as lengths of wing bones (most common elements by far) overlap in their ranges considerably (Worthy & Holdaway 1994) the identity of all small Anas bones need reappraisal.

 In the early 1980s, the entire collection from all Poukawa sites was identified by P. R. Millener, however summary data has not been generated from these identifications (some 20,000 specimens). Recent, reappraisals of some of the identifications show many problems that preclude an accurate assessment of the anatid fauna. Firstly, several rare taxa, have been either overlooked (e.g. Malacorhynchus scarletti), or infrequently recognised (e.g. Mergus, Biziura delautouri). Smaller anatids were generally not identified and were labelled only as ‘anatid sp.’, and where identities were given, much confusion between shoveler, Brown Teal, grey teal and scaup bones is apparent. The Poukawa collection is in urgent need of reappraisal so that the relative frequency of anatids in a prehuman lacustrine fauna can be quantified.

 However, Brown Teal were a very abundant component of the Poukawa fauna. It remains to be seen whether grey teal and shoveler were as abundant as Horn’s data suggests. Throughout the Holocene, Lake Poukawa was a shallow lake surrounded in tall podocarp forest dominated by matai, with a few forest openings (Wilmshurst et al. 1997).

 Inland Wairarapa

Only a single site has revealed Brown Teal bones in the inland karst ranges of the Wairarapa. Karst areas occur mainly in the Waewaepa and Puketoi Ranges near Makuri, and in the Ruakokoputuna-Haurangi Range area. Sites in these regions are mainly pitfall traps. There are two major sites each with thousands of bones: the Coonoor site on the Waewaepa Range is a pitfall trap excavated about 1914, and Martinborough #1 (Haurangi Range) which was discovered in 1901 and excavated at various times, notably 1920, 1956, and in the 1960s. While much material from each site remains to be identified and accessioned into the collections, the many hundreds of bones that have been catalogued probably fairly indicate the composition of the source faunas. Brown teal are only known from Coonoor, and while the fauna is undated, a site in the impure limestone of this area is likely to be geologically young  (a few thousands of years at most) and can be expected to be of Holocene age. The Holocene vegetation in this area was a closed-canopy podocarp forest in a fairly wet climate (c.2000 mm per annum).

 The absence of Brown Teal from Martinborough #1 probably means the species was absent from the surrounds of this site as many hundreds of other individual birds were represented. The site is located on a ridge in the Haurangi Range, which has a much lower rainfall than the Waewaepa Range. Finsch’s duck was common in Martinborough #1 with Millener (1981) recording a minimum of 277 individuals. An extensive series of radiocarbon dates on the site (R. N., Holdaway pers. comm.) indicates the material accumulated only in the last 3000-4000 years, so we can assume the present climate and nearby vegetation is representative of that which surrounded the site during deposition of the fauna. Seasonal drought is common and the nearby forest is dominated by mountain beech (Nothofagus solandri) with a few podocarps such as totara (Podocarpus totara) likely to have been emergent.