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NUMBER 89
the Chatham Island Pied Oystercatcher {Haematopus chathamensis),
also might have become extinct.
Conclusions
Analysis of the abundant and well-dated fossil avian material
found in sand-dune and cave deposits on several of the
larger islands of the Chatham group indicates that these islands
have supported a diverse, highly endemic avifauna since
at least 7000 years ago. This avifauna, some 100 species in
all, including many endemic land and freshwater birds, as
well as a wide variety of seabirds, survived apparently unscathed
until shortly after the first human arrival about 450
years ago.
Many birds of the Chatham Islands exemplify the evolutionary
trend toward larger body size and diminished flying ability
so typically found in small, isolated oceanic-island groups that,
This appendix provides an annotated listing of both conventional
and calibrated radiocarbon ages for samples from
Chatham and Pitt islands. Samples (bone collagen or marineshell
carbonate) are identified by their Rafter Radiocarbon
Laboratory reference numbers (prefixed by NZA). Age data are
presented as follows: conventional age based on the old (Libby)
half-life of 5568 yrs (as "age ± standard deviation yrs BP");
calibrated (corrected) age, given as median age ("CAL BP")
where possible; and calibrated (corrected) age as a range expressed
in terms of the 95% confidence interval (age ± two
standard deviations). Locality names and grid references (GR)
given for sampled sites (see Figure 1, numbered sites 1-21) are
from New Zealand Topographical Map, NZMS 260, 1:50000
metric series, Chatham Islands, edition 1, 1981 (Chatham Island
(localities 1-17), sheet 1; Pitt Island (localities 18-21),
sheet 2 ). (a.s.l.=above sea level.)
CHATHAM ISLAND
Locality 1, Waihora, Point Durham
NZA 3193: Gallirallus dieffenbachii, Sutton coll. WH/VII/2
Layer 1; GR 358470; Waihora Mound site, supposedly midden
material; 5030 ± 68 yrs BP; ca. 5750 CAL BP;
5894-5605 CAL BP.
NZA 3194: Gallirallus dieffenbachii, Sutton coll. WH/VII/
23 Layer 3; GR 358470; Waihora Mound site, supposedly
midden material; 5237 ± 72 yrs BP; ca. 5950 CAL BP;
6173-5753 CAL BP.
Appendix
103
prior to human colonization, lacked mammalian predators.
Most of the Chatham Islands land birds and waterfowl are larger
than their mainland counterparts, and of the 36 prehistorically
known species, at least seven were flightless and three more
would have been weak fliers.
The land birds of the Chatham Islands were clearly no exception
to the general rule that insular species tend to be "naive"
toward humans and introduced predators (Milberg and
Tyrberg, 1993:229). The lethal combination of weak flight and
trusting attitude predisposed them to an extraordinary vulnerability
to human interference. The fossil record of the last 7000
years gives no indication that any of the prehistorically known
species became extinct, or even less abundant, prior to human
arrival. All of the flightless and weak-flying species, and a further
11 flying species, however, became extinct within a few
hundred years of first human settlement through the combined
effects of human perturbations.
Locality 2, Red Bluff
NZA 2610: Hemiphaga chathamica, MNZ S31065; GR
469603; back-beach sequence in embayment, -800 m SSE
of Te Whenuhau Trig, from uppermost stratum of coarse,
yellow, shell sand (beneath windblown fine sand). Indicates
minimum age for >2 m thick sequence; 985 ± 80 yrs BP;
843 CAL BP; 975-689 CAL BP.
Locality 3, Long Beach, S of Henga
limestone bluffs (GR 450655)
NZA 1930: Fulica chathamensis, MNZ S27821; GR 465626;
Long Beach, in typical, stratified, consolidated, dune hummock
(-4 m a.s.l.), immediately beneath eroded surface of
brown sand/soil horizon (30 cm thick), now overlain by
drift sand; 2560 ± 145 yrs BP; 2254 CAL BP; 2666-1924
CAL BP.
NZA 1931: Hemiphaga chathamensis, MNZ S27822; GR
465626; Long Beach, in pale brown sand at 1.5 m depth (directly
underlying sample NZA 1930); 3790 ± 150 yrs BP;
4109 CAL BP; 4511-3697 CAL BP.
NZA 1929: Diaphorapteryx hawkinsi, MNZ S27820; GR
456646; Long Beach, Milton's Gully site, embedded in gray
brown, hard-pan deflation surface (former interdune lake
deposit?); 6660 ± 150 yrs BP; 7456 CAL BP; 7693-7207
CAL BP.
NZA 3246: Hemiphaga chathamensis, MNZ S33158; GR
456646; Long Beach, Milton's Gully site, in horizontally
bedded brown sand at inland margin of and stratigraphically