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NUMBER 89 87
Species
Common Name
Petroica macrocephala chathamensis Chatham Island Tomtit
P. traversi
Black Robin
Anthornis melanura melanocephala Chatham Island Bellbird
TABLE 1.—Continued
Status
B
B
"c. 1906, FB
mass spectrometry (AMS) techniques on avian-bone collagen
or marine-shell carbonate. Within the text, the reported age
given for a specific sample (assigned a Rafter Radiocarbon
Laboratory reference number, prefixed by NZA) is the conventional
radiocarbon age before present (Stuiver and Polach,
1977). Such ages are expressed in the form "age ± standard deviation
(SD) yrs BP." Calibrated ages to which the appropriate
terrestrial or marine calibrations have been applied are expressed
in the form "CAL BP" (see Stuiver and Braziunas,
1993; Stuiver and Pearson, 1993). Within the Appendix, both
conventional and calibrated ages are given for each of the samples
listed. Locality names (see Figure 1) and grid references
for sampled sites are from New Zealand Topographical Map,
New Zealand Map Series (NZMS) 260, 1:50000 series,
Chatham Islands, Edition 1, 1981 (Chatham Island, sheet 1;
Pitt Island, sheet 2).
ACKNOWLEDGMENTS
This research was carried out during my tenure as Curator of
Birds at the Museum of New Zealand (MNZ), Wellington.
Funding for field research and for some radiocarbon dating was
provided by the Museum, and substantial additional funding
for the latter came from several grants from the New Zealand
Lottery Grants Board, through the Lottery Science Research
Committee. All AMS radiocarbon dating was carried out in the
Rafter Radiocarbon Laboratory at the Institute of Geological
and Nuclear Sciences, Gracefield. I am indebted to Rodger
Sparks, Joe McKee, Nicola Redvers-Newton, and Jocelyn
Tumbull for so efficiently processing my numerous radiocarbon
samples. I am grateful to members of the Collection Management
staffs of the Museum of New Zealand, Wellington
(Mike Rudge, Sandy Bartle, Noel Hyde, Raymond Coory), the
Canterbury Museum, Christchurch (Geoff Tunnicliffe), and the
National Museum of Natural History, Smithsonian Institution,
Washington, D.C. (Phil Angle, James Dean) for arranging
loans of, and for access to, specimens in their care. Frank Climo
(MNZ) identified the land snails listed in Table 2.1 thank
Allan Munn and his staff at the Department of Conservation
(DOC) Chatham Island Field Centre, Bruce McFadgen (DOC,
Wellington), and Noel Hyde for assistance with field research.
I also thank Norm Heke (MNZ Photographic Unit) for taking
the photographs. Institutional abbreviations for registration
numbers listed in the Appendix are as follows: Natural History
Museum, London (BMNH; formerly British Museum, Natural
History); National Museum of New Zealand, Wellington (modem
specimens, MNZ; fossil specimens, MNZ S).
Species
Prosthemadera novaeseelandiae
chathamensis
Palaeocorax moriorum
Common Name
Chatham Island Tui
New Zealand Crow
Site Descriptions and Avifaunal Analysis
Status
B
*FB
Our knowledge of the Chatham Islands' prehistoric bird fauna
comes from the detailed examination of the abundant fossil
bones naturally deposited in coastal sand dunes and limestone
caves as well as the archeological material deposited by human
agency in coastal dune middens or dwelling caves. The AMS
radiocarbon dates for more than 60 bone and shell samples (see
Appendix for data and localities) have provided, for the first
time, a sound stratigraphic and radiometric chronology for a
broad selection of avian remains from a variety of depositional
environments. Comparison of these fossil assemblages with the
recent fauna indicates that 21 of the original 36 species of land
birds or waterfowl have become extinct since human settlement
began about 450 years ago (McFadgen, 1994) and that
breeding populations of several seabirds have been reduced or
eliminated. Of the original 100 or so avian taxa recorded, fossil
or living, from the Chathams, only 25 marine and 15 terrestrial
species (a total of 40) now breed there (see Table 1).
Fossil bird bones are known only from Chatham, Pitt, and
Mangere islands. The remaining islands and rock stacks are
typically steeply cliffed and lack extensive sand dunes,
swamps, or caves that could have acted as repositories for
bones.
SAND DUNE SITES
Coastal dune belts, in the form of a series of rows of progradational
sand dunes, generally running parallel to the shore,
and sometimes extending several hundred meters inland of it,
are important physiographic features fringing all but the southern
coasts of Chatham and Pitt islands. These dunes now are
eroded into sequences of discontinuous ridges and hillocks.
They began to form in their present positions only about
6500-7000 years ago, after the sea reached its approximate
current level following the last (Otira) glacial low sea level of
perhaps -120 meters (Hay et al., 1970). At least four depositional
episodes, consisting of unstable phases with high rates of
deposition followed by stable phases with the establishment of
vegetative cover and soil formation, seem to have taken place
over the last 7000 years. It is clear that periodic denudation,
followed by erosion, must have removed parts of the stratigraphic
sequence. Buried soils are frequently exposed as undulating
bands, following the surface contours of the dunes upon
whose surfaces they were formed (Figures 2-5). These soils
consist of variously pale yellow, orange, or chocolate-brown/
black- stained sand up to two meters thick, usually overlain by
unconsolidated drift sand, rapidly deposited and marking the
onset of the first (unstable) phase of the next depositional cy-